Polarization beam splitter and projection apparatus having the same

ABSTRACT

The present invention provides a polarization beam splitter including a multilayer film formed by laminating a first layer having a refractive index in a first range, a second layer having a refractive index in a second range which does not overlap the first range, and a third layer having a refractive index in a third range which does not overlap the first or second range in the order of the first layer, the second layer, the first layer, and the third layer in succession, wherein the transmittance of s-polarized light is 60% or more higher than the transmittance of p-polarized light in a first wavelength region, the transmittance of p-polarized light is equal to or higher than 70% in a second wavelength region different from the first wavelength region, and each of the first wavelength region and the second wavelength region has a bandwidth equal to or larger than 30 nm.

BACKGROUND OF THE INVENTION

The present invention relates to a polarization beam splitter and aprojection apparatus having the same. The present invention relates to apolarization beam splitter with wavelength selectivity which transmitss-polarized light in a first wavelength band and reflects thes-polarized light in a second wavelength band different from the firstwavelength band, and reflects p-polarized light in the first wavelengthband and transmits the p-polarized light in the second wavelength band,by way of example. The present invention is particularly preferable fora projection apparatus which employs a light modulator with liquidcrystal.

A conventionally well-known polarization beam splitter is a polarizationbeam splitter (PBS) of a prism type in which polarization splitting isachieved by a dielectric thin film comprised of a number of alternatelylaminated H layers and L layers between two prisms. Each H layer isformed of a dielectric thin film with high refractive index and each Llayer is formed of a dielectric thin film with low refractive index.

The dielectric thin film has the optical characteristic of transmittingp-polarized light and reflecting s-polarized light incident thereon. Theprinciples of the polarization beam splitter are that, for p-polarizedlight, the incident angle generally matches the Brewster angle θBexpressed by the relationship of the refractive index n_(P) of thematerial of the prism, the refractive index n_(H) of the H layer, andthe refractive index n_(L) of the L layer, thereby transmitting thep-polarized light. For s-polarized light, the reflection at theinterface between the H layer and the L layer is used to reflect thes-polarized light through multilayer film interaction.

The characteristic of the PBS is degraded when it is used out of designconditions due to variations in factors because of a change in incidentangle or wavelength for use. In particular, the conditions for theBrewster angle are sensitive to each constant, so that the p-polarizedlight is more likely to be affected than the s-polarized light.

In an optical system for use in an image projection apparatus (aprojection apparatus), luminous flux radiated from a light source oftenhas a certain angular range, and a wavelength range as wide as the wholerange of visual light is used. In general, the number of the layers inthe polarization splitting film is added or the thickness of the film ismodified to provide favorable characteristics in an intended angularrange and wavelength band.

A PBS which reflects p-polarized light and transmits s-polarized lighthas been reported in “Li Li and J. A. Dobrowolski, Appl. Opt., vol. 39,p. 2754, 2000” (hereinafter referred to as “Document 1”). The incidentangle is set to an angle equal to or larger than the critical angle of aprism with high refractive index (a prism made of a material with highrefractive index) and a thin film with low refractive index (a thin filmmade of a material with low refractive index) to produce attenuatedtotal reflection. Since the light after attenuated total reflection hasits phase changed, the principles of transmitting p-polarized light andreflecting s-polarized light through interference in a providedmultilayer film are used to realize the PBS. This achieves favorablecharacteristics in a wide range of incident angles.

On the other hand, a dichroic filter is also well-known which has adielectric thin film comprised of alternately laminated H layers eachformed of a dielectric thin film with high refractive index and L layerseach formed of a dielectric thin film with low refractive index.

The dichroic film also has the optical characteristic of utilizinginterference in the multilayer film through reflection at the interfacebetween the H layer and the L layer to transmit or reflect light in aspecific wavelength band. A variety of film structures are known whichrealize the functions of a high pass filter, a low pass filter, a bandpass filter or the like. In particular, to separate the wavelength bandsfor red, green, and blue from each other, it is possible to use a longwavelength transmission filter, a wavelength band pass filter, a shortwavelength transmission filter or the like. The characteristic of thedichroic filter is degraded when the incident angle and polarizationconditions are out of design conditions.

When the incident angle is changed, the optical admittance of the thinfilm material is changed to widen the transmission band of p-polarizedlight (or narrow the reflection band) and narrow the transmission bandof s-polarized light (or widen the reflection band). As a result, thetransition wavelengths at the shift from the transmission band to thereflection band are changed in opposite directions in the p-polarizedlight and s-polarized light.

Thus, design is typically made such that the number of the layers in thepolarization splitting film is added or the thickness of the film ismodified to widen the angular range for use and reduce the polarizationdependence in p-polarized light and s-polarized light. On the contrary,design may be made by taking advantage of the difference incharacteristics depending on polarization.

The PBS or dichroic filter is used to form a colorseparation/combination optical system (a color separation/colorcombination means) of an image projection apparatus.

FIG. 27 shows an example of a conventional image projection apparatuswhich employs a light modulator of a reflection type realized withliquid crystal.

Arrows represent the optical paths of light beams for red, green, andblue in white display (image information is for white color). Solidlines represent s-polarized light, while broken lines representp-polarized light.

White light emits from a light source 51, and unified into s-polarizedlight by a polarization changer 52. A dichroic mirror 53 a transmits alight beam 30 in a green wavelength band, and reflects a light beam 40in a red wavelength band and a light beam 20 in a blue wavelength band.

The light beam 30 in the green wavelength band transmitted through thedichroic mirror 53 a is reflected by a PBS 54 a, incident on areflection type light modulator 55 g realized with liquid crystal forgreen, and modulated. For the white display, the modulated light emergestherefrom as p-polarized light 31 which is then transmitted through thePBS 54 a and a PBS 54 c and is incident on a projection lens system (aprojection optical system) 57 for projection.

The light beam 20 in the blue wavelength band reflected by the dichroicmirror 53 a is changed into p-polarized light 21 by a wavelengthselective phase shifter 56 b, transmitted through a PBS 54 b, andincident on a reflection type light modulator 55 b realized with liquidcrystal for blue and then modulated.

For the white display, the modulated light emerges therefrom ass-polarized light 20, so that it is reflected by the PBS 54 b andmaintained as the s-polarized light 20 through a wavelength selectivephase shifter 56 r. It is then reflected by the PBS 54 c and is incidenton the projection lens system 57 for projection.

The light beam 40 in the red wavelength band reflected by the dichroicmirror 53 a is maintained as the s-polarized light 40 through thewavelength selective phase shifter 56 b, reflected by the PBS 54 b, andincident on a reflection type light modulator 55 r realized with liquidcrystal for red, and then modulated. For the white display, since themodulated light emerges therefrom as p-polarized light 41, it istransmitted through the PBS 54 b, changed into s-polarized light 40through the wavelength selective phase shifter 56 r, reflected by thePBS 54 c, and incident on the projection lens system 57 for projection.

For black display (image information is for black color), all of thelight beams emerge from the reflection type light modulators 55 r, 55 g,or 55 b with the same polarization as when they are incident thereon, sothat they return toward the light source 51 along the same optical pathsthrough the respective optical members. The color separation/combinationmeans as described above is used to take advantage of the reflectiontype light modulator realized with the liquid crystal with highresolution and to form a small apparatus.

The conventional PBS aims to transmit p-polarized light and reflects-polarized light throughout the wavelength band for use. The PBSdescribed in Document 1 reflects p-polarized light and transmitss-polarized light. All of the PBSs are devices for providingpolarization splitting throughout the wavelength band for use. None ofthe previously reported PBSs has wavelength selectivity or haspolarization splitting characteristics reversed in different wavelengthbands such that it transmits s-polarized light and reflects p-polarizedlight in a first wavelength band and reflects s-polarized light andtransmits p-polarized light in a second wavelength band different fromthe first wavelength band.

In the dichroic filter, the transmission band of p-polarized light iswidened and the transmission band of s-polarized light is narrowed whenlight is obliquely incident thereon, so that polarization splitting isperformed in a certain wavelength band. However, p-polarized light istransmitted and s-polarized light is reflected at all times, andp-polarized light is not reflected and s-polarized light is nottransmitted. Thus, it does not have the characteristic depending onwavelength such that it transmits s-polarized light and reflectsp-polarized light in a first wavelength band and reflects s-polarizedlight and transmits p-polarized light in a second wavelength banddifferent from the first wavelength band.

The color separation/combination in the image projection apparatus shownin FIG. 27 requires the two wavelength selective phase shifters 56 b and56 r. Each of the wavelength selective phase shifters 56 b and 56 r iscomprised of a plurality of laminated stretched polycarbonate films withbirefringence such that their anisotropy axes are arranged at particularangles, as described in U.S. Pat. No. 5,658,490 (hereinafter referred toas “Document 2”). It involves a more complicated fabricating method andthus is an expensive optical device as compared with the PBS or dichroicfilter formed with the dielectric thin film using a deposition method.

Since the polycarbonate is a polymer film, it is highly susceptible tothe influence of external environment such as heat, humidity, andultraviolet rays in view of the physical property of the material, andthe reliability and durability of the color separation/combination meansmay be reduced. In addition, the low surface accuracy may cause flare ifit is used in an optical system. On the other hand, depending on ananti-reflection film, each of the projection lenses reflects some amountof light, and the reflected light returns toward the colorseparation/combination means as return light. In the conventional colorseparation/combination means, the return light reaches the lightmodulator realized with liquid crystal and thus causes flare.

Japanese Patent Laid-Open No. 11-504441 (hereinafter referred to as“Document 3”) has disclosed a projection apparatus which employs areflection type light modulator realized with liquid crystal without awavelength selective phase shifter. Document 3 has disclosed a colorseparation/combination means which employs a PBS having the effect ofreflecting p-polarized light and transmitting s-polarized light in ablue wavelength band and transmitting p-polarized light and reflectings-polarized light in green and red wavelength bands. However, the PBS isonly described in terms of its functions, and a method of realizing ithas not been disclosed.

A polarization beam splitter with wavelength selectivity (a wavelengthselective polarization beam splitter) which transmits s-polarized lightand reflects p-polarized light in a first wavelength band and reflectss-polarized light and transmits p-polarized light in a second wavelengthband different from the first wavelength band has not been realized.

It is an object of the present invention to provide a wavelengthselective polarization beam splitter which transmits s-polarized lightand reflects p-polarized light in a first wavelength band and reflectss-polarized light and transmits p-polarized light in a second wavelengthband different from the first wavelength band.

It is another object of the present invention to realize a projectionapparatus which employs the wavelength selective polarization beamsplitter as a color separation/color combination means (a colorseparation/combination system) of the projection apparatus to simplifythe structure and achieve high contrast with excellent reliability anddurability.

BRIEF SUMMARY OF THE INVENTION

According to an aspect, the present invention provides a polarizationbeam splitter including a multilayer film formed by laminating a firstlayer having a refractive index in a first range, a second layer havinga refractive index in a second range which does not overlap the firstrange, and a third layer having a refractive index in a third rangewhich does not overlap the first or second range in the order of thefirst layer, the second layer, the first layer, and the third layer,wherein the transmittance of s-polarized light is 60% or more higherthan the transmittance of p-polarized light in a first wavelengthregion, the transmittance of p-polarized light is equal to or higherthan 70% in a second wavelength region different from the firstwavelength region, and each of the first wavelength region and thesecond wavelength region has a bandwidth equal to or larger than 30 nm.

According to another aspect, the present invention provides an imagedisplay apparatus including a first image display device, a second imagedisplay device, and a color combination optical system which combinesfirst image light emerging from the first image display device andsecond image light emerging from the second image display device,wherein the color combination optical system has the polarization beamsplitter according to the abovementioned aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and 1(b) schematically show the basic operation(characteristic) of a polarization beam splitter with wavelengthselectivity, and specifically, FIG. 1(a) shows s-polarized light andFIG. 1(b) shows p-polarized light.

FIG. 2(a) shows the simulation result of the angular characteristic oftransmittance of s-polarized light and p-polarized light at a wavelengthof 500 nm in the film structure expressed asPrism|1.0L0.5H1.0M0.5H|Adhesive when an incident-side prism is made of amaterial having a refractive index of 1.85, an H layer has a refractiveindex of 2.32, an L layer has a refractive index of 1.39, an M layer hasa refractive index of 1.65, and an adhesive with a refractive index of1.55 is used on the emergence side. FIG. 2(b) shows the simulationresult of the angular characteristic of transmittance of s-polarizedlight and p-polarized light at a wavelength of 550 nm in the filmstructure expressed as Prism|(1.0L0.5H1.0M0.5H)¹⁰|Adhesive when theincident-side prism is made of a material having a refractive index of1.85, the H layer has a refractive index of 2.32, the L layer has arefractive index of 1.39, the M layer has a refractive index of 1.65,and the adhesive with a refractive index of 1.55 is used on theemergence side.

FIG. 3 shows the simulation result of the wavelength characteristic oftransmittance of s-polarized light and p-polarized light at an incidentangle of 45 degrees in the film structure expressed asPrism|(1.0L0.5H1.0M0.5H)¹⁰|Adhesive when the incident-side prism is madeof a material having a refractive index of 1.85, the H layer has arefractive index of 2.32, the L layer has a refractive index of 1.39,the M layer has a refractive index of 1.65, and the adhesive with arefractive index of 1.55 is used on the emergence side.

FIG. 4 shows the simulation result of transmittance of s-polarized lightand p-polarized light in the wavelength selective polarization beamsplitter in Example 1.

FIG. 5(a) shows the simulation result of the angular characteristic oftransmittance of s-polarized light and p-polarized light at a wavelengthof 500 nm in the film structure expressed asPrism|0.7L0.35H1.5M0.35H|Adhesive when an incident-side prism is made ofa material having a refractive index of 1.85, an H layer has arefractive index of 2.32, an L layer has a refractive index of 1.39, anM layer has a refractive index of 1.65, and an adhesive with arefractive index of 1.55 is used on the emergence side. FIG. 5(b) showsthe simulation result of the angular characteristic of transmittance ofs-polarized light and p-polarized light at a wavelength of 500 nm in thefilm structure expressed as Prism|(0.7L0.35H1.5M0.35H)¹⁰|Adhesive at awavelength of 550 nm when the incident-side prism is made of a materialhaving a refractive index of 1.85, the H layer has a refractive index of2.32, the L layer has a refractive index of 1.39, the M layer has arefractive index of 1.65, and the adhesive with a refractive index of1.55 is used on the emergence side.

FIG. 6 shows the simulation result of the wavelength characteristic oftransmittance of s-polarized light and p-polarized light at an incidentangle of 45 degrees in the film structure expressed asPrism|(0.7L0.35H1.5M0.35H)¹⁰|Adhesive at a wavelength of 550 nm when theincident-side prism is made of a material having a refractive index of1.85, the H layer has a refractive index of 2.32, the L layer has arefractive index of 1.39, the M layer has a refractive index of 1.65,and the adhesive with a refractive index of 1.55 is used on theemergence side.

FIG. 7 shows the simulation result of transmittance of s-polarized lightand p-polarized light in a wavelength selective polarization beamsplitter in Example 2.

FIG. 8 shows the simulation result of transmittance of s-polarized lightand p-polarized light in a third multilayer film in Example 3.

FIG. 9 shows the simulation result of transmittance of s-polarized lightand p-polarized light in a wavelength selective polarization beamsplitter in Example 3.

FIG. 10 shows the simulation result of transmittance of s-polarizedlight and p-polarized light in a wavelength selective polarization beamsplitter in Example 4.

FIG. 11 shows the simulation result of transmittance of s-polarizedlight and p-polarized light in a wavelength selective polarization beamsplitter in Example 5.

FIG. 12 shows the simulation result of transmittance of s-polarizedlight and p-polarized light in a wavelength selective polarization beamsplitter in Example 6.

FIG. 13 shows the simulation result of transmittance of s-polarizedlight and p-polarized light in a wavelength selective polarization beamsplitter in Example 7.

FIG. 14(a) shows the simulation result of the angular characteristic oftransmittance of s-polarized light and p-polarized light at a wavelengthof 500 nm in the film structure expressed asPrism|2.1M1.2L2.1M0.6H|Adhesive at a wavelength of 550 nm when anincident-side prism is made of a material having a refractive index of1.85, an H layer has a refractive index of 2.32, an L layer has arefractive index of 1.39, an M layer has a refractive index of 1.65, andan adhesive with a refractive index of 1.55 is used on the emergenceside. FIG. 14(b) shows the simulation result of the angularcharacteristic of transmittance of s-polarized light and p-polarizedlight in the film structure expressed asPrism|(2.1M1.2L2.1M0.6H)¹⁰|Adhesive at a wavelength of 550 nm when theincident-side prism is made of a material having a refractive index of1.85, the H layer has a refractive index of 2.32, the L layer has arefractive index of 1.39, the M layer has a refractive index of 1.65,and the adhesive with a refractive index of 1.55 is used on theemergence side.

FIG. 15 shows the simulation result of the wavelength characteristic oftransmittance of s-polarized light and p-polarized light at an incidentangle of 45 degrees in the film structure expressed asPrism|(0.6H2.1M1.2L2.1M)¹⁰|Adhesive at a wavelength of 550 nm when theincident-side prism is made of a material having a refractive index of1.85, the H layer has a refractive index of 2.32, the L layer has arefractive index of 1.39, the M layer has a refractive index of 1.65,and the adhesive with a refractive index of 1.55 is used on theemergence side.

FIG. 16 shows the simulation result of transmittance of s-polarizedlight and p-polarized light in a wavelength selective polarization beamsplitter in Example 8.

FIG. 17 shows the simulation result of transmittance of s-polarizedlight and p-polarized light in a third multilayer film in Example 9.

FIG. 18 shows the simulation result of transmittance of s-polarizedlight and p-polarized light in a wavelength selective polarization beamsplitter in Example 10.

FIG. 19 shows the simulation result of the wavelength characteristic oftransmittance of s-polarized light and p-polarized light at an incidentangle of 45 degrees in the film structure expressed asPrism|(0.5L1.7M0.5L0.5H)¹⁰|Adhesive at a wavelength of 550 nm when anincident-side prism is made of a material having a refractive index of1.85, an H layer has a refractive index of 2.32, an L layer has arefractive index of 1.39, an M layer has a refractive index of 1.65, andan adhesive with a refractive index of 1.55 is used on the emergenceside.

FIG. 20 shows the simulation result of transmittance of s-polarizedlight and p-polarized light in a wavelength selective polarization beamsplitter in Example 11.

FIG. 21 shows the simulation result of the wavelength characteristic oftransmittance of s-polarized light and p-polarized light at an incidentangle of 45 degrees in the film structure expressed asPrism|(0.5L1.9M0.5L0.32H)¹⁰|Adhesive at a wavelength of 550 nm when anincident-side prism is made of a material having a refractive index of1.85, an H layer has a refractive index of 2.32, an L layer has arefractive index of 1.39, an M layer has a refractive index of 1.65, andan adhesive with a refractive index of 1.55 is used on the emergenceside.

FIG. 22 shows the simulation result of transmittance of s-polarizedlight and p-polarized light in a wavelength selective polarization beamsplitter in Example 12.

FIG. 23 shows the simulation result of transmittance of s-polarizedlight and p-polarized light in a wavelength selective polarization beamsplitter in Example 13.

FIG. 24 shows an image projection apparatus which employs the wavelengthselective polarization beam splitter and a reflection type lightmodulator realized with liquid crystal in Example 14.

FIG. 25 shows an image projection apparatus which employs the wavelengthselective polarization beam splitter and a reflection type lightmodulator realized with liquid crystal in Example 15.

FIG. 26(a) and 26(b) show an image projection apparatus which employsthe wavelength selective polarization beam splitter and a reflectiontype light modulator realized with liquid crystal in Example 14, andspecifically, FIG. 26(a) shows the optical paths for white display andFIG. 26(b) shows the optical paths of return light from a projectionlens system.

FIG. 27 shows a conventional liquid crystal projection apparatus whichemploys a reflection type light modulator realized with liquid crystal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments will hereinafter be described.

A polarization beam splitter of each of the embodiments includes amultilayer film formed by laminating a first layer having a refractiveindex in a first range, a second layer having a refractive index in asecond range which does not overlap the first range, and a third layerhaving a refractive index in a third range which does not overlap thefirst or second range in the order of the first layer, the second layer,the first layer, and the third layer (in succession). The polarizationbeam splitter has transmittance of s-polarized light (at least 70% ormore) which is 60% or more higher than the transmittance of p-polarizedlight (at least 30% or less) in a first wavelength region (a regionhaving a band of at least 30 nm or more from 450 to 480 nm, and morepreferably, from 440 to 485 nm) and has transmittance of p-polarizedlight equal to or higher than 70% in a second wavelength band (a regionhaving a band of at least 30 nm or more from 600 to 630 nm, and morepreferably, from 590 to 640 nm) different from the first wavelengthband. Each of the first wavelength region and the second wavelengthregion has a bandwidth equal to or larger than 30 nm. Alternatively, thepolarization beam splitter has transmittance of s-polarized light 60% ormore higher than the transmittance of p-polarized light in a firstwavelength region (preferably at least part of a blue wavelength regionfrom 400 to 500 nm) and has transmittance of p-polarized light 60% ormore higher than the transmittance of s-polarized light in a secondwavelength band (preferably at least part of a red wavelength regionfrom 570 to 700 nm) different from the first wavelength band. Each ofthe first wavelength region and the second wavelength region has abandwidth equal to or larger than 30 nm.

The multilayer film is a multilayer film formed by laminating the firstlayer, the second layer, the first layer, and the third layer in thisorder in succession five times or more.

The first wavelength region and the second wavelength region areincluded in region of visible wavelength (400 nm or higher and 700 nm orlower). The first wavelength region includes a band of 450 nm to 480 nmand the second wavelength region includes a band of 600 nm to 630 nm.

When a layer of the first, second, and third layers with the highestrefractive index is an H layer (a high refractive index layer), a layerof the three layers with the second highest refractive index is an Mlayer (a middle refractive index layer), and a layer of the three layerswith the lowest refractive index is an L layer (a low refractive indexlayer), then the high refractive index layer has a refractive index of2.0 or higher and 2.6 or lower, the middle refractive index layer has arefractive index of 1.59 or higher and 1.9 or lower, and the lowrefractive index layer has a refractive index of 1.25 or higher and 1.56or lower.

In the polarization beam splitter in claim 7 according to any one ofclaims 1 to 6, when a layer of the first, second, and third layers withthe highest refractive index is an H layer (a high refractive indexlayer), a layer of the three layers with the second highest refractiveindex is an M layer (a middle refractive index layer), and a layer ofthe three layers with the lowest refractive index is an L layer (a lowrefractive index layer), then the difference in the refractive indexbetween the high refractive index layer and the middle refractive indexlayer is 0.35 or higher and 0.9 or lower, and the difference in therefractive index between the middle refractive index layer and the lowerrefractive index layer is 0.12 or higher and 0.55 or lower.

The multilayer film is sandwiched between a substance made of a firstmaterial having a refractive index of 1.55 or higher and 2.10 or lowerand a substance made of a second material having a refractive index of1.40 or higher and 1.70 or lower.

At least one of the first layer, the second layer, and the third layerincludes two layers having refractive indexes different from each other.

The first range corresponds to the highest range of refractive indexesof the first, second, and third ranges. In the polarization beamsplitter, when a layer of the first, second, and third layers with thehighest refractive index is an H layer, a layer of the three layers withthe second highest refractive index is an M layer, a layer of the threelayers with the lowest refractive index is an L layer, the refractiveindexes of the H layer, L layer, and M layer are represented as n_(H),n_(L), and n_(M), a design wavelength is represented as λ, themultilayer film is formed by laminating the first H layer, the M layer,the second H layer, and the L layer in this order in succession, and thefilm thickness of the first H layer, the M layer, the second H layer,and the L layer are represented as b×λ/(4n_(H)), c×λ/(4n_(M)),d×λ/(4n_(H)), a×λ/(4n_(L)), then 0<a<3, 0<b<1, 0<c<5, and 0<d<1 aresatisfied.

In the polarization beam splitter, when a layer of the first, second,and third layers with the highest refractive index is an H layer, alayer of the three layers with the second highest refractive index is anM layer, a layer of the three layers with the lowest refractive index isan L layer, the refractive indexes of the H layer, L layer, and M layerare represented as n_(H), n_(L), and n_(M), a design wavelength isrepresented as λ, the multilayer film is formed by laminating the firstH layer, the M layer, the second H layer, and the L layer in this orderin succession, and the film thickness of the first H layer, the M layer,the second H layer, and the L layer are represented as b×λ/(4n_(H)),c×λ/(4n_(M)), d×λ/(4n_(H)), a×λ/(⁴n_(L)), then 0<b≦a≦c<5, 0<d≦a≦c<5 aresatisfied.

The first range corresponds to the second highest range of refractiveindexes of the first, second, and third ranges. In the polarization beamsplitter, when a layer of the first, second, and third layers with thehighest refractive index is an H layer, a layer of the three layers withthe second highest refractive index is an M layer, a layer of the threelayers with the lowest refractive index is an L layer, the refractiveindexes of the H layer, L layer, and M layer are represented as n_(H),n_(L), and n_(M), a design wavelength is represented as λ, themultilayer film is formed by laminating the first M layer, the L layer,the second M layer, and the H layer in this order in succession, and thefilm thickness of the first M layer, the L layer, the second M layer,and the H layer are represented as a×λ/(4n_(M)), b×λ/(4n_(L)),c×λ/(4n_(M)), d×λ/(4n_(H)), then 0<a<6, 0<c<6, d<b, 0<b<5, and 0<d<2 aresatisfied.

When a layer of the first, second, and third layers with the highestrefractive index is an H layer, a layer of the three layers with thesecond highest refractive index is an M layer, a layer of the threelayers with the lowest refractive index is an L layer, the refractiveindexes of the H layer, L layer, and M layer are represented as n_(H),n_(L), and n_(M), a design wavelength is represented as λ, themultilayer film is formed by laminating the first M layer, the L layer,the second M layer, and the H layer in this order in succession, and thefilm thickness of the first M layer, the L layer, the second M layer,and the H layer are represented as a×λ/(4n_(M)), b×λ/(4n_(L)),c×λ/(4n_(M)), d×λ/(4n_(H)), then 0<a<3, 0<c<6, d<b, 0<b<2, and 0<d<1 aresatisfied.

The first range corresponds to the lowest range of refractive indexes ofthe first, second, and third ranges. In the polarization beam splitter,when a layer of the first, second, and third layers with the highestrefractive index is an H layer, a layer of the three layers with thesecond highest refractive index is an M layer, a layer of the threelayers with the lowest refractive index is an L layer, the refractiveindexes of the H layer, L layer, and M layer are represented as n_(H),n_(L), and n_(M), a design wavelength is represented as λ, themultilayer film is formed by laminating the first L layer, the H layer,the second L layer, and the M layer in this order in succession, and thefilm thickness of the first L layer, the H layer, the second L layer,and the M layer are represented as a×λ/(4n_(L)), b×λ/(4n_(H)),c×λ/(4n_(L)), d×λ/(4n_(M)), then 0<a<3, 0<b<5, d<b, 0<c<3, and 0<d<1 aresatisfied.

In the polarization beam splitter in claim 18 according to claim 16 or17, when a layer of the first, second, and third layers with the highestrefractive index is an H layer, a layer of the three layers with thesecond highest refractive index is an M layer, a layer of the threelayers with the lowest refractive index is an L layer, the refractiveindexes of the H layer, L layer, and M layer are represented as n_(H),n_(L), and n_(M), a design wavelength is represented as λ, themultilayer film is formed by laminating the first L layer, the H layer,the second L layer, and the M layer in this order in succession, and thefilm thickness of the first L layer, the H layer, the second L layer,and the M layer are represented as a×λ/(4n_(L)), b×λ/(4n_(H)),c×λ/(4n_(L)), d×λ/(4n_(M)), then 0<b≦a≦c<5, 0<d≦a≦c<5 are satisfied.

According to an aspect, the present invention provides an image displayapparatus includes a first image display device, a second image displaydevice, and a color combination optical system which combines firstimage light emerging from the first image display device and secondimage light emerging from the second image display device, wherein thecolor combination optical system has the polarization beam splitter asdescribed above.

According to another aspect, the present invention provides an imagedisplay apparatus including a first reflection type liquid crystaldisplay device which is provided for first color light, a secondreflection type liquid crystal display device which is provided forsecond color light different from the first color light, an illuminationoptical system which illuminates the first and second reflection typeliquid crystal display devices with light from a light source, and aprojection optical system which projects light from the first and secondreflection type liquid crystal display devices to a projected surface,wherein the illumination optical system includes the polarization beamsplitter as described above, and the first color light in a firstpolarization state and the second color light in the first polarizationstate are directed to the polarization beam splitter to illuminate thefirst reflection type liquid crystal display device with the first colorlight in the first polarization state and illuminate the secondreflection type liquid crystal display device with the second colorlight in the first polarization state, and the polarization beamsplitter color-combines the first color light in a second polarizationstate and the second color light in the second polarization stateemerging from the first reflection type liquid crystal display deviceand the second reflection type liquid crystal display device,respectively, to direct the combined light to the projection opticalsystem, the second polarization state showing a polarization directionorthogonal to the first polarization state.

Examples of the present invention will hereinafter be described indetail with reference to the drawings.

EXAMPLE 1

FIGS. 1(a) and 1(b) are schematic diagrams showing the main portions ofa polarization beam splitter with wavelength selectivity (a wavelengthselective polarization beam splitter) of Example 1. FIGS. 1(a) and 1(b)simply illustrate the characteristic of the wavelength selectivepolarization beam splitter. The wavelength selective polarization beamsplitter 1 of Example 1 is formed by bonging a prism on an incident side(an optical member) 11 and a prism on an emergence side (an opticalmember) 12. A multilayer film structure 10 with a structure describedlater is provided on a plane inclined 45 degrees with respect to anincident surface 110 of the incident-side prism 11 and an emergencesurface 121 of the emergence-side prism 12.

Luminous flux incident on the multilayer film structure 10 of thewavelength selective polarization beam splitter 1 has an incident angle(in design) of 45 degrees (in other words, it has almost idealcharacteristics for light incident thereon at an incident angle of 45degrees). The characteristic of the wavelength selective polarizationbeam splitter 1 depends on the polarization direction and wavelengthband. The wavelength selective polarization beam splitter 1 has thecharacteristic of higher transmittance of s-polarized light than that ofp-polarized light for light in a wavelength range (lower reflectance ofs-polarized light than that of p-polarized light), and lowertransmittance of s-polarized light than that of p-polarized light forlight in a wavelength range different from that wavelength region(higher reflectance of s-polarized light than that of p-polarizedlight).

It is assumed that a light beam 20 of s-polarized light in a bluewavelength band (in a wavelength band of at least 450 to 480 nm, andpreferably, 445 to 480 nm) and a light beam 40 of s-polarized light in ared wavelength band (in a wavelength band of at least 600 to 630, andpreferably, 590 to 640 nm) are incident on the wavelength selectivepolarization beam splitter 1. In this case, as shown in FIG. 1(a), thelight beam 20 in the blue wavelength band is transmitted through themultilayer structure 10 and emerges from the emergence surface 121,while the light beam 40 in the red wavelength band is reflected by themultilayer film structure 10 and emerges from an emergence surface 111.As shown in FIG. 1(b), when a light beam 21 of p-polarized light in theblue wavelength band and a light beam 41 of p-polarized light in the redwavelength band are incident thereon, the light beam 21 in the bluewavelength band is reflected by the multilayer film structure 10 andemerges from the emergence surface 111, while the light beam 41 in thered wavelength band is transmitted through the multilayer structure 10and emerges from the emergence surface 121 as shown in FIG. 1(b).

The multilayer film structure 10 provided for the wavelength selectivepolarization beam splitter 1 of Example 1 is formed to include amultilayer film provided by laminating three kinds of thin films, thatis, an H layer with high refractive index, an L layer with lowrefractive index, an M layer with middle refractive index between thoseof the H and L layers, in the order of H, M, H, and L. The refractiveindex of each layer and the thickness of the film can be appropriatelyset as described below to provide a polarization beam splitter whichtransmits s-polarized light and reflects p-polarized light in awavelength band.

The polarization beam splitter 1 is comprised of the incident-side prism11 made of a material with a refractive index of 1.85, the multilayerfilm provided closer to the emergence side than the incident-side prism11 and made of three (or four or more) kinds of materials with differentrefractive indexes from each other, that is, the high refractive indexlayer (hereinafter referred to as the “H layer”) made of a material witha refractive index of 2.32, the low refractive index layer (hereinafterreferred to as the “L layer”) made of a material with a refractive indexof 1.39, and the middle refractive index layer (hereinafter referred toas the “M layer”) made of a material with a refractive index of 1.65,and an adhesive with a refractive index of 1.55 provided on theemergence side of the multilayer film.

The refractive indexes of the materials of the H layer, L layer, and Mlayer are represented as n_(H), n_(L), and n_(M). The thicknesses of theH layer, L layer, and M layer (the actual thicknesses, not the distancesof air determined from conversion) are represented as d_(H), d_(L), andd_(M). The design wavelength (550 nm in this case) is represented as λ.The quarter wavelength thicknesses of the H layer, L layer, and M layer(H=λ/(4n_(H)) for the H layer, L=d_(L)=λ/(4n_(L)) for the L layer,M=λ/(4n_(M)) for the M layer) are represented as H, L, and M. In thiscase, FIG. 2(a) shows the angular characteristic of the transmittance ofs-polarized light and p-polarized light at a wavelength of 550 nm in themultilayer film structure formed by laminating the incident-side prism,1.0×L, 0.5×H, 1.0×M, 0.5×H, and the adhesive (hereinafter such amultilayer film structure is represented as“Prism|1.0L0.5H1.0M0.5H|Adhesive”) in order from the incident side. Theincident prism and the adhesive provided on the emergence side may bemade of different materials as long as the same refractive indexes aremaintained (for example, the adhesive and the prism may be provided onthe incident side and the emergence side, respectively).

In FIG. 2(a), the transmittance of s-polarized light is larger than thatof p-polarized light at incident angles of 42 to 44 degrees, althoughthe difference is small. FIG. 2(b) shows the angular characteristic ofthe transmittance of s-polarized light and p-polarized light at awavelength of 550 nm in a polarization beam splitter having a multilayerfilm of 10 repetitions of the arrangement comprised of the L layer, Hlayer, M layer, and H layer (or the H layer, M layer, H layer, and Llayer). The structure of the polarization beam splitter having themultilayer film of 10 repetitions of the arrangement of the L layer, Hlayer, M layer, and H layer is represented as“Prism|(1.0L0.5H1.0M05.H)¹⁰|Adhesive.”

As compared with FIG. 2(a), the difference in transmittance betweens-polarized light and p-polarized light is increased to show the obviouspolarization splitting. FIG. 3 shows the wavelength characteristic ofthe transmittance in the multilayer film at an incident angle of 45degrees. The multilayer film basically shows the characteristic of anedge filter in which a transmission band and a reflection bandalternately appear, and it is characterized by significant polarizationsplitting in the s-polarized light and p-polarized light. Thesignificant polarization splitting is used to provide the characteristicthat s-polarized light is transmitted and p-polarized light is reflectedin the blue wavelength band (a first wavelength band), while s-polarizedlight is reflected and p-polarized light is transmitted in the redwavelength band (a second wavelength band). In other words, the basiccharacteristic of the wavelength selective polarization beam splitter isshown. As a result of study, the multilayer film structure satisfies thefollowing relationship for the basic film structure, and the refractiveindex of each layer and the film thickness are appropriately selected,thereby allowing an excellent polarization beam splitter. Specifically,a multilayer film or a polarization beam splitter having the multilayerfilm is designed to satisfy 0<a<3, 0<b≦1, 0<c<5, 0<d≦1 (a, b, c, and dare real numbers) when the thicknesses of the H layer, M layer, H layer,and L layer laminated repeatedly in the first multilayer film describedabove are set to b×H, c×M, d×H, and a×L, respectively.

It is also possible to provide a multilayer film or a polarization beamsplitter with a more favorable angular characteristic when themultilayer film structure of the first multilayer film is formed tosatisfy the relationship: 0<a<1.5, 0<b≦1, 0<c<2, 0<d≦1 (a, b, c, and dare real numbers).

However, some ripple is found in the transmission wavelength band (anincident angle of 45 degrees) in FIG. 3. The film thickness was adjusted(optimized) in order to reduce the ripple and adjust the wavelengthband. PBH56 (product name) manufactured by OHARA Inc. (the materialthereof having a refractive index of 1.85 at a wavelength of 550 nm) wasused for the incident prism 11, TiO₂ (with a refractive index of 2.32 ata wavelength of 550 nm) was used for the H layer, MgF₂ (with arefractive index of 1.39 at a wavelength of 550 nm) was used for the Llayer, Al₂O₃ (with a refractive index of 1.65 at a wavelength of 550 nm)was used for the M layer, and an adhesive with a refractive index of1.55 was used on the emergence side. In each of Examples describedbelow, the same materials can be used for the H layer, L layer, and Mlayer.

Table 1 shows the film thickness of each layer of the first multilayerfilm after the adjustment of the film thickness. FIG. 4 shows thetransmittance characteristic (at an incident angle of 45 degrees) of thepolarization beam splitter having the multilayer layer. In Table 1, thenumber of a layer represents the order from the incident side. As seenfrom Table 1, the number of the layers in the first multilayer layer was40 in total.

As apparent from FIG. 4, it is possible to provide the polarization beamsplitter (the wavelength selective polarization beam splitter) in which,for the light in the blue wavelength range (particularly 440 to 480 nm)of the light incident on the first multilayer film at an incident angleof 45 degrees, the transmittance of s-polarized light is 60% or morehigher than that of p-polarized light (s-polarized light is transmittedand p-polarized light is reflected), and for the light in the redwavelength band (particularly 580 to 660 nm), the transmittance ofp-polarized light is 60% or more higher than that of s-polarized light(s-polarized light is reflected and p-polarized light is transmitted).

The number of layers and the film thickness are not limited to thosedescribed in Table 1. Even when the film thickness is changed somewhat,or one or two films not described in Table 1 are included in themultilayer film, it can be considered as falling within substantiallythe same scope as that described in Example 1.

While the optimizing method is used to reduce the ripple, it is possibleto design a monolayer or a multilayer as an adjusting layer and optimizea multilayer film by arranging the adjusting layer. Since the equivalentoptical characteristic can also be provided when a conventional filmdesign method is used such as a symmetric multilayer film structure, theoptimization method is not limited to that described in Example 1.

The number of necessary layers depends on the specifications of thepolarization splitting value, the central angle for use, and the angularrange for use. Thus, the present invention is not limited to the numberof layers described in Table 1 or other Tables.

It is possible to provide a layer with no optical effect or slightoptical effect between the adjacent ones of the H layer, M layer, and Llayer. For example, the layer may be provided to satisfy the followingexpression generally:nd≦2 nmwhere n represents the refractive index and d represents the thickness.

The H layer is the thin film layer having the refractive index fallingwithin the highest range of refractive indexes. The M layer is the thinfilm layer having the refractive index falling within the range ofrefractive indexes lower than those of the H layer. The L layer is thethin film layer having the refractive index falling within the range ofrefractive indexes lower than those of the M layer. Thus, in themultilayer film structure having the repetitions of the arrangement ofthe L layer, H layer, M layer, and H layer, the H layer has the higherrefractive index than those of the adjacent thin films, the L layer hasthe lower refractive index than those of the adjacent thin films, andthe M layer has the higher refractive index than that of one of theadjacent thin films and the lower refractive index than that of theother of the adjacent thin films. It goes without saying that each ofthe H layer, M layer, and L layer does not need to be made of a singlekind of material, and a plurality of materials may be used as long asthey have refractive indexes falling within the associated ranges.

In the multilayer film structure of Example 1, it is desirable that thearrangement of the L layer, H layer, M layer, and H layer (or themultilayer film including the H layer, M layer, H layer, and L layer inthis order) is repeated ten times or more (at least five times)(preferably, they are repeatedly laminated without any other layerssandwiched).

The multilayer film (the first multilayer film) has the opticalcharacteristic of having high transmittance of s-polarized light in thefirst wavelength band and low transmittance of s-polarized light in thesecond wavelength band different from the first wavelength band, and lowtransmittance of p-polarized light in the first wavelength band and hightransmittance of p-polarized light in the second wavelength band. It isdesirable that each of the first wavelength band and the secondwavelength band has a bandwidth of 30 nm or more (preferably 50 nm ormore) and the difference in transmittance between s-polarized light andp-polarized light is 60% or higher (preferably 75% or higher) in each ofthe first wavelength region and the second wavelength region each havingthe bandwidth of 30 nm or more.

As shown in FIGS. 1(a) and 1(b), the wavelength selective polarizationbeam splitter has the multilayer film structure 10 disposed between theincident-side prism 11 and the emergence-side prism 12. Reflectionoccurs on the bonding surface of the adhesive and the prism on which themultilayer film is not disposed. The reflection reduces thetransmittance in the transmission band. It is thus preferable to providean anti-reflection structure on the bonding surface of the prism and theadhesive. As the anti-reflection structure, a well-known monolayer ormultilayer anti-reflection film or the like can be used.

The polarization beam splitter described in Example 1 and otherpolarization beam splitters described in Examples below hardly absorblight in the visible region. While only the “transmittance” is describedin each FIG. which show the transmittance of the polarization beamsplitter provided herein, the “reflectance” of the polarization beamsplitter can be easily found since the polarization beam splittersdescribed in Examples hardly absorb light in the visible region.Although the “reflectance” of the polarization beam splitter is notparticularly described in each figure or the like, it can essentially beconsidered to be described by assuming“100%−(transmittance)≈(reflectance).” The absorption rate of light ofthe visible region in the polarization beam splitter (the absorptionrate of white light in which light at wavelengths of 400 to 700 nm ispresent substantially uniformly) is 2% at most, and preferably 0.5% orlower.

The foregoing explanation applies to each of Examples described below.

For reference, the real numbers a, b, c, and d will be calculated fromTable 1.

As described above, n_(H), n_(L), n_(M) represent the refractive indexesof the materials of the H layer, L layer, and M layer, and λ the designwavelength. Since H=λ/(4n_(H)), L=d_(L)=λ/(4n_(L)), M=λ/(4n_(M)), thethicknesses of the L layer, H layer, M layer, and H layer are determinedas a×λ/(4n_(L)), b×λ/(4n_(H)), o×λ/(4n_(M)), and d×λ/(4n_(H)),respectively.

First, the relationship between the film thickness d_(L) of the L layerwith low refractive index as the first layer and the real number a isdetermined as follows. From d_(L)=a×λ/(4n_(L)), a=d_(L)×λ/(4n_(L))/λ iscalculated. With reference to Table 1, d_(L)=70.66 (nm), λ=550 (nm), andn_(L)=1.39 are substituted to determine a=0.714.

The real number b for the H layer with high refractive index as thesecond layer is calculated as follows. Specifically, d_(H)=26.45 (nm),λ=550 (nm), and n_(H)=2.32 are substituted in b=d_(H)×(4n_(H))/λ, andthen b=0.446 is determined.

The real number c for the M layer with middle refractive index as thethird layer is calculated as follows. Specifically, d_(M)=96.53 (nm),λ=550 (nm), and n_(M)=1.65 are substituted in c=d_(M)×(4n_(M))/λ, andthen c=1.158 is determined.

The real number d for the H layer with high refractive index as thefourth layer is calculated as follows. Specifically, d_(H)=39.69 (nm),λ=550 (nm), and n_(H)=2.32 are substituted in d=d_(H)×(4n_(H))/λ, andthen d=0.670 is determined.

The real numbers a to d can be determined for respective layers with thecalculations as described above.

While the real numbers a to d show the values of the numeric range inthe respective layers, the splitting characteristic is not significantlychanged even when the real numbers a to d are out of the numeric rangesthereof in some of the plurality of layers.

Thus, the average values of the real numbers a to d can be used as a′,b′, c′, and d′ in the respective layers laminated in the order of thelow refractive index layer, high refractive index layer, middlerefractive index layer, and high refractive index layer.

The calculations of the real numbers a to d and the use of the averagevalues a′, b′, c′, and d′ in the numeric range apply to each of Examplesdescribed below.

EXAMPLE 2

The multilayer layer (referred to as the first multilayer layer) shownin Table 1 of Example 1 is designed for a particular incident angle (45degrees in Example 1). As seen in the angular characteristic in FIG.2(b), the optical characteristic such as the transmittancecharacteristic and reflection characteristic is sensitively changed inresponse to a change in angle (a shift of the incident angle from thedesign incident angle, that is, 45 degrees in Example 1). To addressthis, in Example 2, a polarization beam splitter (a multilayer layer) isdesigned to be less sensitive to (resistant to) a change in angle ascompared with Example 1.

This is because the incident angle of luminous flux incident on a colorseparation/combination means (a polarization beam splitter for use in acolor separation/combination system or the like) of a projectionapparatus such as a projector has a predetermined distribution, and someof the light is incident thereon at an angle different from the designvalue (for example, 45 degrees).

A second multilayer layer, later described, can be put on the firstmultilayer layer described above to provide a polarization beam splitterwith an excellent angular characteristic. The second multilayer film isa multilayer film provided by laminating three kinds of thin films, thatis, an H layer with high refractive index, an L layer with lowrefractive index, and an M layer with middle refractive index betweenthose of the H layer and L layer, in the order of the L layer, H layer,M layer, and H layer (naturally, any of them may be the first layer. Inother words, the order of the H layer, M layer, H layer, and L layer maybe used, for example). It has high transmittance of s-polarized light inthe blue wavelength band, low transmittance of p-polarized light in theblue wavelength band, and high transmittance of p-polarized light in thered wavelength band.

FIG. 5(a) shows the angular characteristic of the transmittance ofs-polarized light and p-polarized light at a wavelength of 500 nm in apolarization beam splitter in which an incident-side prism 11 is made ofa material with a refractive index of 1.85, the H layer has a refractiveindex of 2.32, the L layer has a refractive index of 1.39, the M layerhas a refractive index of 1.65, an adhesive with a refractive index of1.55 is provided on the emergence side, and the structure of thepolarization beam splitter is represented generally as“Prism|0.7L0.35H1.5M0.35H|Adhesive” at a wavelength of 550 nm. Thetransmittance of s-polarized light is larger than that of p-polarizedlight at incident angles of 40 to 48 degrees, although the different isslight.

FIG. 5(b) shows the angular characteristic of transmittance ofs-polarized light and p-polarized light in a polarization beam splitterhaving 10 repetitions of the abovementioned multilayer film structureand represented as “Prism=51 (0.7L0.35H1.5M0.35H)¹⁰|Adhesive.” Ascompared with FIG. 5(a), the difference in transmittance betweens-polarized light and p-polarized light is increased to show the obviouspolarization splitting. FIG. 6 shows the wavelength characteristic oftransmittance in the second multilayer film at an incident angle of 45degrees. Similarly to FIG. 3 for the first multilayer film, it basicallyshows the characteristic of an edge filter in which a transmission bandand a reflection band alternately appear, and significant polarizationsplitting is seen in s-polarized light and p-polarized light. The secondmultilayer film is further characterized by adjusting the refractiveindex and the film thickness to transmit s-polarized light in thereflection band thereof (the band of approximately 500 to 650 nm). Thiscan be used to transmit s-polarized light and reflect p-polarized lightgenerally in the blue wavelength band (a first wavelength band), andtransmit s-polarized light and p-polarized light in the red wavelengthband (a second wavelength band), that is, provide the basiccharacteristic of the second multilayer layer.

When multilayer films with shifted design wavelengths are laminated forthe second multilayer film, s-polarized light is hardly affected(although ripple is larger) since it is transmitted throughout thewavelength band (at wavelengths of approximately 420 nm to 650 nm), andonly the blocking wavelength band of p-polarized light is widened. Thus,the second multilayer film can be put on another multilayer film toreduce only the transmittance of p-polarized light in the bluewavelength band as a whole. In this manner, the first multilayer filmcan be put on the second multilayer film to provide a multilayer filmhaving a wavelength selective polarization splitting function with anexcellent angular characteristic or a polarization beam splitter (awavelength selective polarization beam splitter) having the multilayerlayer.

The polarization beam splitter can be provided with an excellent angularcharacteristic by forming the multilayer film such that the following issatisfied:0<b≦a≦c<5, 0<d≦a≦c<5 (a, b, c, and d are real numbers)when the thicknesses of the H layer, M layer, H layer, and L layerlaminated repeatedly in the second multilayer film are set to b×H, c×M,d×H, and a×L, respectively.

More preferably, the following is satisfied:0<b≦a≦c<2, 0<d≦a≦c<2

The second multilayer film intended to increase the blocking band at asmall incident angle as described above is put on the first multilayerfilm, and the film thickness is adjusted (optimized) in order to reduceripple and adjust the wavelength band. PBH56 (product name) manufacturedby OHARA Inc. (the material thereof having a refractive index 1.85 at awavelength of 550 nm) was used for the incident-side prism 11, TiO₂(with a refractive index of 2.32 at a wavelength of 550 nm) was used forthe H layer, MgF₂ (with a refractive index of 1.39 at a wavelength of550 nm) was used for the L layer, Al₂O₃ (with a refractive index 1.65 ata wavelength of 550 nm) was used for the M layer, and an adhesive with arefractive index of 1.55 was used on the emergence side. The number oflayers was 103 in total. Table 2 shows each film thickness in themultilayer film and the polarization beam splitter having the multilayerfilm. FIG. 7 shows the transmittance characteristic of the polarizationbeam splitter for s-polarized light and p-polarized light incident at anincident angle of 45±5 degrees. As seen in FIG. 7, in the range ofincident angles of 45±5 degrees (substantially throughout the range ofincident angles of 40 to 50 degrees), it is possible to provide thepolarization beam splitter (the wavelength selective polarization beamsplitter) which has transmittance of s-polarized light in the bluewavelength band (especially 440 to 480 nm) 60% or more higher than thetransmittance of p-polarized light (transmitting s-polarized light andreflecting p-polarized light) and the transmittance of p-polarized lightin the red wavelength band (especially 590 to 640 nm) 60% or more higherthan the transmittance of s-polarized light (reflecting s-polarizedlight and transmitting p-polarized light).

EXAMPLE 3

In Example 3, a third multilayer film is designed to have the opticalcharacteristic of high transmittance of s-polarized light in the bluewavelength band (a first wavelength band) and low transmittance ofs-polarized light in the red wavelength band (a second wavelength band),and high transmittance of p-polarized light in the red wavelength band.The third multilayer film is put on the second multilayer film used inExample 2 (the film having high transmittance of s-polarized light andlow transmittance of p-polarized light in the blue wavelength band andhigh transmittance of p-polarized light in the red wavelength band) toform a polarization beam splitter film.

The third multilayer film can be realized by satisfying the Brewsterangle determined from the refractive index of the multilayer film forthe incidence of p-polarized light and functioning as a dichroic filterfor the incident of s-polarized light. In addition, it can also bedesigned by adjusting the cut-off wavelength of s-polarized light andp-polarized light in the dichroic filter.

Table 3 shows an example of the third multilayer layer. FIG. 8 shows thetransmittance characteristic (changes in transmittance) when light inthe visible region (400 to 700 nm) is incident on the third multilayerlayer at incident angles of 40, 45, and 50 degrees. PBH56 (product name)manufactured by OHARA Inc. (the material thereof having a refractiveindex of 1.85 at a wavelength of 550 nm) was used for an incident prism,TiO₂ (with a refractive index of 2.32 at a wavelength of 550 nm) wasused for an H layer, SiO₂ (with a refractive index of 1.49 at awavelength of 550 nm) was used for an L layer (an L2 layer, laterdescribed), Al₂O₃ (with a refractive index of 1.65 at a wavelength of550 nm) was used for an M layer, and an adhesive with a refractive indexof 1.55 was used on the emergence side. In the design example of thethird multilayer film, the number of layers is 24 in total (naturally,the number of layers may be other than 24). It can be seen from FIG. 8showing the transmittance characteristic of the third multilayer filmthat it transmits s-polarized light in the blue wavelength band andreflects s-polarized light in the red wavelength band incident on thethird multilayer film (the polarization beam splitter including theincident-side prism and the adhesive on the emergence side) at anincident angle of 45±5 degrees (substantially in the range of angles of40 to 50 degrees) and transmits p-polarized light in the red wavelengthband (also transmits p-polarized light in the blue wavelength band)incident on the third multilayer film (the polarization beam splitterincluding the incident-side prism and the adhesive on the emergenceside) at an incident angle of 45±5 degrees (substantially in the rangeof angles of 40 to 50 degrees).

The second multilayer film is put on the third multilayer film to form amultilayer film for use in the polarization beam splitter of Example 3.In the specific design, the number of layers was increased to increasethe blocking bandwidth of the second multilayer film (the band in whichs-polarized light is transmitted and p-polarized light is reflected),and the film thickness was adjusted (optimized) to reduce ripple andadjust the wavelength band. In a polarization beam splitter whichemploys the multilayer film after the adjustment of the film thickness,PBH56 (product name) manufactured by OHARA Inc. (the material thereofhaving a refractive index 1.85 at a wavelength of 550 nm) was used forthe incident-side prism, TiO₂ (with a refractive index of 2.32 at awavelength of 550 nm) was used for the H layer, MgF₂ (with a refractiveindex of 1.39 at a wavelength of 550 nm) was used for the L1 layer, SiO₂(with a refractive index of 1.49 at a wavelength of 550 nm) was used forthe L2 layer, Al₂O₃ (with a refractive index 1.65 at a wavelength of 550nm) was used for the M layer, and an adhesive with a refractive index of1.55 was used for the material on the emergence side. Of the multilayerfilm used in the polarization beam splitter, the multilayer filmcomprised of the H, M, H, and L1 layers including the H layer, M layer,and L1 layer corresponds to the abovementioned second multilayer film,while the multilayer film comprised of the H layer, M layer, and L2layer corresponds to the abovementioned third multilayer film. Thenumber of layers is 144 in total. The L1 layer and L2 layer are includedin the L layer (the layer with low refractive index) in a broad sense.An Hi layer and an H2 layer, later described, are included in the Hlayer, and an M1 layer and an M2 layer are included in the M layer.

Table 4 shows the film thickness of each layer in the polarization beamsplitter thus designed. FIG. 9 shows the transmittance characteristic(the transmittance characteristic for light in the visible region) ofs-polarized light and p-polarized light incident on the multilayer filmof the polarization beam splitter at an incident angle of 45±5 degrees.As can be seen from FIG. 9, it is possible to provide the polarizationbeam splitter (the wavelength selective polarization beam splitter)which has transmittance of s-polarized light 60% or more higher than thetransmittance of p-polarized light in the blue wavelength range(especially 435 to 490 nm) (transmitting s-polarized light andreflecting p-polarized light) and the transmittance of p-polarized light60% or more higher than the transmittance of s-polarized light in thered wavelength band (especially 590 to 640 nm) (reflecting s-polarizedlight and transmitting p-polarized light).

EXAMPLE 4

In Example 1 to 3, the first wavelength band (the band in which thepolarization beam splitter transmits s-polarized light and reflectsp-polarized light) is the blue wavelength band, while the secondwavelength band (the band in which the polarization beam splittertransmits p-polarized light and reflects s-polarized light) is the redwavelength band. In contrast, in Example 4, the red wavelength band isused as a first wavelength band, while the blue wavelength band is usedas a second wavelength band. In design, similarly to Example 3, thesecond multilayer film was put on the third multilayer film, and thefilm thickness was optimized. Table 5 shows the thickness of each filmresulting from the design and FIG. 10 shows the transmittance at anincident angle of 45±5 degrees.

PBH56 (product name) manufactured by OHARA Inc. (the material thereofhaving a refractive index 1.85 at a wavelength of 550 nm) was used foran incident-side prism, TiO₂ (with a refractive index of 2.32 at awavelength of 550 nm) was used for an H layer, MgF₂ (with a refractiveindex of 1.39 at a wavelength of 550 nm) was used for an L1 layer, SiO₂(with a refractive index of 1.49 at a wavelength of 550 nm) was used foran L2 layer, Y₂O₃ (with a refractive index of 1.80) was used for an M1layer, Al₂O₃ (with a refractive index 1.65 at a wavelength of 550 nm)was used for an M2 layer, and an adhesive with a refractive index of1.55 was used on the emergence side.

A multilayer film formed by repeatedly laminating H, M, H, and L (L1)including the H layer, M1 layer, and L1 layer was used as the secondmultilayer film. A multilayer comprised of the H layer, M2 layer, and L2layer was used as the third multilayer film. The number of layers is 164in total. In the angular range of 45±5 degrees, s-polarized light isreflected and p-polarized light is transmitted in the blue wavelengthband, while s-polarized light is transmitted and p-polarized light isreflected in the red wavelength band. It can be seen that favorablecharacteristics are provided both in the separation of the wavelengthbands and the excellent polarization splitting.

In this manner, the wavelength selective polarization beam splitter isnot limited to a particular wavelength band and can providecharacteristics based on the specifications. The wavelength band can beshifted by uniformly changing the film thickness of all the layers, aswell known.

EXAMPLE 5

In Example 5, MgF₂ is not used for an L layer, but SiO₂, which is widelyused as a material of a thin film with low refractive index, is used. Indesign, similarly to Example 2, the first multilayer film was put on thesecond multilayer film, and the film thickness was optimized.

Table 6 shows each film thickness resulting from the design and FIG. 11shows the transmittance at an incident angle of 45±5 degrees. PBH56(product name) manufactured by OHARA Inc. (the material thereof having arefractive index 1.85 at a wavelength of 550 nm) was used for anincident-side prism, TiO₂ (with a refractive index of 2.32 at awavelength of 550 nm) was used for an H layer, SiO₂ (with a refractiveindex of 1.49 at a wavelength of 550 nm) was used for an L layer, Y₂O₃(with a refractive index of 1.80) was used for an M layer, and anadhesive with a refractive index of 1.55 was used on the emergence side.The number of layers is 203 in total. In the angular range of 45±5degrees, s-polarized light is transmitted and p-polarized light isreflected in the blue wavelength band, while s-polarized light isreflected and p-polarized light is transmitted in the red wavelengthband. It can be seen that favorable characteristics are provided both inthe separation of the wavelength bands and the excellent polarizationsplitting. Since SiO₂ has higher refractive index than MgF₂, the numberof layers is increased as compared with the case where MgF₂ is used. Thesame applies to the H layer. The H layer can be designed by using a thinfilm made of Ta₂O₅ or the like, not TiO₂. In this manner, the thin filmfor realizing the wavelength selective polarization beam splitter is notlimited to a particular material.

EXAMPLE 6

In Example 6, PBH56 (product name) is not used for an incident-sideprism but S-LAL14 (product name) manufactured by OHARA Inc., which is atype of glass with lower refractive index, is used. In design, similarlyto Examples 2 and 5, the first multilayer film was put on the secondmultilayer film, and the film thickness was optimized.

Table 7 shows each film thickness resulting from the design and FIG. 12shows the transmittance at an incident angle of 45±5 degrees. S-LAL14(product name) manufactured by OHARA Inc. (the material thereof having arefractive index 1.70 at a wavelength of 550 nm) was used for anincident-side prism, TiO₂ (with a refractive index of 2.32 at awavelength of 550 nm) was used for an H layer, MgF₂ (with a refractiveindex of 1.39 at a wavelength of 550 nm) was used for an L layer, Al₂O₃(with a refractive index of 1.65 with a wavelength of 550 nm) was usedfor an M layer, and an adhesive with a refractive index of 1.55 was usedon the emergence side. The number of layers is 232 in total.

In the angular range of 45±5 degrees, s-polarized light is transmittedand p-polarized light is reflected in the blue wavelength band, whiles-polarized light is reflected and p-polarized light is transmitted inthe red wavelength band. It can be seen that favorable characteristicsare provided both in the separation of the wavelength bands and theexcellent polarization splitting. Since S-LAL14 (product name) has lowerrefractive index than PBH56 (product name), the number of layers isincreased as compared with the case where PBH56 (product name) is used.However, the polarization beam splitter is not limited to particularglass on the incident side.

EXAMPLE 7

In Example 7, two H layers are made of different materials in design ofrepetitions of the basic film arrangement comprised of an L layer, Hlayer, M layer, and H layer in this order. The basic film arrangementcomprised of an L layer, H1 layer, M layer, and H2 layer in this orderis repeated in Example 7.

In design, similarly to Examples 2, 5 and 6, the first multilayer filmwas put on the second multilayer film, and the film thickness wasoptimized. Table 8 shows each film thickness resulting from the designand FIG. 13 shows the transmittance at an incident angle of 45±5degrees. PHB56 (product name) manufactured by OHARA Inc. (the materialthereof having a refractive index 1.85 at a wavelength of 550 nm) wasused for an incident-side prism, TiO₂ (with a refractive index of 2.32at a wavelength of 550 nm) was used for the H1 layer, Ta₂O₅ (with arefractive index of 2.15 at a wavelength of 550 nm) was used for the H2layer, MgF₂ (with a refractive index of 1.39 at a wavelength of 550 nm)was used for the L layer, Al₂O₃ (with a refractive index of 1.65 with awavelength of 550 nm) was used for the M layer, and an adhesive with arefractive index of 1.55 was used on the emergence side. The number oflayers is 151 in total.

In the angular range of 45±5 degrees, s-polarized light is transmittedand p-polarized light is reflected in the blue wavelength band, whiles-polarized light is reflected and p-polarized light is transmitted inthe red wavelength band. It can be seen that favorable characteristicsare provided both in the separation of the wavelength bands and theexcellent polarization splitting. Thus, it can be found that the samekind of thin film is not necessarily required in repeating thearrangement of L, H, M, and H. It is also possible to use a differentthin film material for each repetition, for example, in the order of L,H1, M, H1, L, H2, M, and H2. The same applies to the M layer and Llayer.

EXAMPLE 8

Examples 2 to 7 have shown that the second multilayer film is realizedby laminating the three kinds of thin films, that is, the H layer withhigh refractive index, the L layer with low refractive index, and the Mlayer with middle refractive index between those of the H and L layers,in the order of the L layer, H layer, M layer, and H layer, andadjusting the refractive index and the film thickness. The presentinventors have studied the second multilayer film and found that thesimilar characteristics to those of the second multilayer film can berealized by a fifth multilayer film formed by laminating three kinds ofthin films, that is, an H layer with high refractive index, an L layerwith low refractive index, and an M layer with middle refractive indexbetween those of the H and L layers, in the order of the M layer, Llayer, M layer, and H layer, and adjusting the refractive index and thefilm thickness.

The fifth multilayer film is a multilayer film of the L, M, H, and Mlayers and has the optical characteristic of high transmittance ofs-polarized light and low transmittance of p-polarized light in a firstwavelength band, and high transmittance in a second wavelength banddifferent from the first wavelength band. Each of the first wavelengthband and the second wavelength band has a bandwidth of 30 nm or more andincludes a band in which the difference in transmittance is 60% orhigher between s-polarized light and s-polarized light.

S-LAH55 (product name) manufactured by OHARA Inc. was used for anincident-side prism 11 and the material thereof has a refractive indexof 1.84, the H layer (the material of the H layer) has a refractiveindex of 2.32, the L layer (the material of the L layer) has arefractive index of 1.39, the M layer (the material of the M layer) hasa refractive index of 1.65, and an adhesive with a refractive index of1.55 was used on the emergence side to bond two prisms. FIG. 4(a) showsthe angular characteristic of the transmittance of s-polarized light andp-polarized light at a wavelength of 500 nm in the film structureexpressed as Prism|2.1M1.2L2.1M0.6H|Adhesive at a wavelength of 550 nm.

The transmittance of s-polarized light is higher than that ofp-polarized light at incident angles of 42 to 45 degrees, although thedifference is slight. FIG. 14(b) shows the angular characteristic of thetransmittance of s-polarized light and p-polarized light in thestructure of 10 repetition of the abovementioned multilayer filmarrangement, expressed as Prism|(2.1M1.2L2.1M0.6H)¹⁰|Adhesive.

As compared with FIG. 14(a), the difference in transmittance betweens-polarized light and p-polarized light is increased and obviouspolarization splitting is shown. FIG. 15 shows the wavelengthcharacteristic of the transmittance at an incident angle of 45 degreesin the multilayer film.

Similarly to FIG. 6 in Example 2, it basically shows the characteristicof an edge filter in which a transmission band and a reflection bandalternately appear, and it is characterized by significant polarizationsplitting in s-polarized light and p-polarized light. The significantpolarization splitting can be used to transmit s-polarized light andreflect p-polarized light generally in the blue wavelength band (thefirst wavelength band) and transmit s-polarized light and p-polarizedlight in the red wavelength band (the second wavelength band), that is,provide the basic characteristic of the fifth multilayer film. Ascompared with FIG. 6, the reflectance of p-polarized light is reducedeven with the same number of layers. Thus, the number of layers in themultilayer film is reduced as compared with the case where the L layer,H layer, M layer, and H layer are repeated. On the other hand, it can beseen that the angular characteristic is sensitive, and the number oflayers is increased when the range of incident angles is widened.

When multilayer films with shifted design wavelengths are laminated forthe fifth multilayer film, s-polarized light is hardly affected(although ripple is larger) since it is transmitted throughout thewavelength band (approximately wavelengths of 420 nm to 650 nm), andonly the blocking wavelength band of p-polarized light is widened. Thus,the fifth multilayer film can be put on another multilayer film toreduce only the transmittance of p-polarized light in the bluewavelength band as a whole.

As a result, a fourth multilayer film is formed as a multilayer filmincluding an M layer, L layer, M layer, and H layer, in which it hashigh transmittance of s-polarized light in a first wavelength band andlow transmittance in a second wavelength band different from the firstwavelength band, and low transmittance of p-polarized light in the firstwavelength band and high transmittance in the second wavelength band,each of the first wavelength band and the second wavelength band has abandwidth of 30 nm or more, and the first wavelength band includes aband in which the difference in transmittance between s-polarized lightand p-polarized light is 60% or higher. The fourth multilayer film canbe put on the fifth multilayer to provide a polarization beam splitterwith an excellent angular characteristic.

The result of study has shown that the polarization beam splitter can beprovided with an excellent angular characteristic by satisfying thefollowing relationship for the basic film structure in the fourth andfifth multilayer films and appropriately selecting the refractive indexand film thickness of each layer:(a×M b×L c×M d×H)0<a<6, 0<c<6, d<b, 0<b<5, 0<d<2where a, b, c, and d are real numbers, H the symbol for representing thequarter wavelength thickness of the layer with high refractive index ofd_(H)=/λ(4n_(H)), L the symbol for representing the quarter wavelengththickness of the layer with low refractive index of d_(L)=/λ(4n_(L)), Mthe symbol for representing the quarter wavelength thickness of thelayer with middle refractive index of d_(M)=/λ(4n_(M)), n_(H), n_(L),and n_(M) the refractive indexes of the H layer, L layer, and M layer,respectively, d_(H), d_(L), and d_(M) the film thickness of the H layer,L layer, and M layer, and λ the design wavelength.

In addition, the polarization beam splitter can be provided with a moreexcellent angular characteristic by satisfying the followingrelationship for the basic film structure in the multilayer filmstructure and appropriately selecting the refractive index and filmthickness of each layer:(a×M b×L c×M d×H)0<a<3, 0<c<3, d<b, 0<b<2, 0<d<1

In specific design, the fifth multilayer film including an increasednumber of layers for widening the blocking band at a small incidentangle was put on the first multilayer film, and the thickness wasoptimized in order to reduce ripple and adjust the wavelength band.

S-LAH55 (product name) manufactured by OHARA Inc. (with a refractiveindex 1.84 at a wavelength of 550 nm) was used for the incident-sideprism 11, TiO₂ (with a refractive index of 2.32 at a wavelength of 550nm) was used for the H layer, MgF₂ (with a refractive index of 1.39 at awavelength of 550 nm) was used for the L layer, Al₂O₃ (with a refractiveindex 1.65 at a wavelength of 550 nm) was used for the M layer, and anadhesive with a refractive index of 1.55 was used on the emergence side.The number of layers is 65 in total. Table 9 shows the thickness of eachfilm. FIG. 16 shows the transmittance at an incident angle of 45±2degrees. In the angular range of 45±2 degrees, s-polarized light istransmitted and p-polarized light is reflected in the blue wavelengthband, and s-polarized light is reflected and p-polarized light istransmitted in the red wavelength band, which shows favorablecharacteristics both in the separation of the wavelength bands and theexcellent polarization splitting.

EXAMPLE 9

In Example 8, the three kinds of thin films, that is, the H layer withhigh refractive index, the L layer with low refractive index, the Mlayer with medium refractive index between those of the H and L layersare laminated in the order of M, L, M, and H, and then the refractiveindex and film thickness are adjusted, thereby providing the fifthmultilayer film. The fifth multilayer film was put on the fourthmultilayer film. A polarization beam splitter in Example 9 is formed byputting the fifth multilayer film formed of the lamination of the Mlayer, L layer, M layer, and H layer on the third multilayer film.

The third multilayer film has the optical characteristic of hightransmittance of s-polarized light in a first wavelength band, lowtransmittance in a second wavelength band, and high transmittance ofp-polarized light in the second wavelength band.

In specific design, the number of layers was increased to widen theblocking band in the fifth multilayer film, and the film thickness wasoptimized to reduce ripple and adjust the wavelength band. S-LAH55(product name) manufactured by OHARA Inc. (with a refractive index 1.84at a wavelength of 550 nm) was used for an incident-side prism, TiO₂(with a refractive index of 2.32 at a wavelength of 550 nm) was used forthe H layer, MgF₂ (with a refractive index of 1.39 at a wavelength of550 nm) was used for the L layer, Al₂O₃ (with a refractive index 1.65 ata wavelength of 550 nm) was used for the M layer, and an adhesive with arefractive index of 1.55 was used on the emergence side. The number oflayers is 63 in total. Table 10 shows the resulting thickness of eachfilm. FIG. 17 shows the transmittance at an incident angle of 45±2degrees. In the angular range of 45±2 degrees, s-polarized light istransmitted and p-polarized light is reflected in the blue wavelengthband, and s-polarized light is reflected and p-polarized light istransmitted in the red wavelength band, which shows favorablecharacteristics both in the separation of the wavelength bands and theexcellent polarization splitting.

EXAMPLE 10

The wavelength selective polarization beam splitter of the presentinvention has the multilayer film structure 10 disposed between theincident-side prism 11 and the emergence-side prism 12 as shown in FIGS.1(a) and 1(b). Thus, reflection occurs on the bonding surface of theadhesive and the prism on which the multilayer film is not disposed. Thereflection reduces the transmittance in the transmission band.Countermeasures against this include the anti-reflection structureprovided on the bonding surface of the prism and the adhesive asdescribed above. In Example 10, the first multilayer film is separatelyput on the sides of the incident-side prism 11 and the emergence-prism12, and they are bonded together with an adhesive. Since theintermediate adhesive is an non-interfering medium, the design needs tobe made in view of that. The fifth multilayer film and the thirdmultilayer film which constitute the first multilayer film are put foreach of the prisms on the incident side and emergence side. Since therespective films are designed with separate functions, the design iseasily performed and advantages in manufacture can be provided.

In specific design, S-LAH55 (product name) manufactured by OHARA Inc.(with a refractive index 1.84 at a wavelength of 550 nm) was used forthe incident-side and emergence-side prisms, Ta₂O₅ (with a refractiveindex of 2.15 at a wavelength of 550 nm) was used for the H layer of thethird multilayer film, Al₂O₃ (with a refractive index of 1.65 at awavelength of 550 nm) was used for the L layer of the third multilayerfilm, the adhesive with a refractive index of 1.55 was used on theemergence side, TiO₂ (with a refractive index 2.32 at a wavelength of550 nm) was used for the H layer of the fifth multilayer film, MgF₂(with a refractive index of 1.39 at a wavelength of 550 nm) was used forthe L layer of the fifth multilayer film, and Al₂O₃ (with a refractiveindex of 1.65 at a wavelength of 550 nm) was used for the M layer of thefifth multilayer film. The number of layers is 63 in the fifthmultilayer film and 13 in the third multilayer film. Tables 11 and 12show the thickness of each film. FIG. 18 shows the transmittance at anincident angle of 45±2 degrees in all the films including the thirdmultilayer film and fifth multilayer film. Transmittance T wascalculated by using the following expression which takes account of themultiple reflection in the adhesive of the non-interfering medium:$\begin{matrix}{T = \frac{1}{{1/T_{1}} + {1/T_{2}} - 1}} & \lbrack {{EQUATION}\quad 1} \rbrack\end{matrix}$where T1 and T2 represent the transmittances of the third multilayerfilm and fifth multilayer film, respectively. From the transmittances,s-polarized light is transmitted and p-polarized light is reflected inthe blue wavelength band, and s-polarized light is reflected andp-polarized light is transmitted in the red wavelength band in theangular range of 45±2 degrees. Thus, it can be seen that favorablecharacteristics are provided both in the separation of the wavelengthbands and the excellent polarization splitting.

When the multilayer film is separately provided on the incident side andemergence side, it is possible to use design different from that ofExample 10 in which it is separately provided for different functions,and the present invention is not limited thereto. The equivalent opticalcharacteristic can also be achieved when a symmetric multilayer filmstructure is used, and in this case, the same films are used on theincident side and the emergence side, so that the same process canadvantageously be used to form the films. The present invention is notlimited to the abovementioned structures.

EXAMPLE 11

Example 1 has shown that the first multilayer film can be realized bylaminating the three kinds of thin films, that is, the H layer with highrefractive index, the L layer with low refractive index, the M layerwith medium refractive index between those of the H and L layers in theorder of L, H, M, and H, and then adjusting the refractive index andfilm thickness. The present inventors have studied the first multilayerfilm and found that the similar characteristics to those of the secondmultilayer film can be realized by a sixth multilayer film provided bylaminating three kinds of thin films, that is, an H layer with highrefractive index, an L layer with low refractive index, an M layer withmedium refractive index between those of the H and L layers in the orderof L, M, L and H, and then adjusting the refractive index and filmthickness.

The sixth multilayer film is a multilayer film of L, M, L, and H layersand has the optical characteristic of high transmittance of s-polarizedlight in a first wavelength band and low transmittance in a secondwavelength band different from the first wavelength band, and lowtransmittance of p-polarized light in the first wavelength band and hightransmittance in the second wavelength band. Each of the firstwavelength band and the second wavelength band has a bandwidth of 30 nmor more and includes a band in which the difference in transmittance is60% or higher between s-polarized light and p-polarized light.

S-LAH55 (product name) manufactured by OHARA Inc. was used for anincident-side prism 11 and the material thereof has a refractive index1.84, the H layer (the material of the H layer) has a refractive indexof 2.32, the L layer (the material of the L layer) has a refractiveindex of 1.39, the M layer (the material of the M layer) has arefractive index of 1.65, and an adhesive with a refractive index of1.55 was used on the emergence side to bond two prisms. FIG. 19 showsthe wavelength characteristic of the transmittance of s-polarized lightand p-polarized light at an incident angle of 45 degrees in the filmstructure expressed as Prism|(0.5L1.7M0.5L0.5H)¹⁰|Adhesive at awavelength of 550 nm.

Similarly to FIG. 3 in Example 1, it basically shows the characteristicof an edge filter in which a transmission band and a reflection bandalternately appear, and it is characterized by significant polarizationsplitting in s-polarized light and p-polarized light. The significantpolarization splitting can be used to provide the characteristic oftransmitting s-polarized light and reflecting p-polarized light in theblue wavelength band (the first wavelength band) and reflectings-polarized light and transmitting p-polarized light in the redwavelength band (the second wavelength band), that is, provide the basiccharacteristic of the wavelength selective polarization beam splitter.

The result of study has shown that the excellent polarization beamsplitter can be achieved by satisfying the following relationship forthe basic film structure in the sixth multilayer film and appropriatelyselecting the refractive index and film thickness of each layer:(a×L b×M c×L d×H)0<a<3, 0<b<5, 0<c<3, 0<d<1where a, b, c, and d are real numbers, H the symbol for representing thequarter wavelength thickness of the layer with high refractive index ofd_(H)=/λ(4n_(H)), L the symbol for representing the quarter wavelengththickness of the layer with low refractive index of d_(L)=/λ(4n_(L)), Mthe symbol for representing the quarter wavelength thickness of thelayer with middle refractive index of d_(M)=/λ(4n_(M)), nH, nL, and nMthe refractive indexes of the H layer, L layer, and M layer,respectively, d_(H), d_(L), and d_(M) the film thickness of the H layer,L layer, and M layer, and k the design wavelength.

In addition, the polarization beam splitter can be provided with a moreexcellent angular characteristic by satisfying the followingrelationship for the basic film structure in the multilayer structureand appropriately selecting the refractive index and film thickness ofeach layer:(a×L b×M c×L d×H)0<a<1.5, 0<b<2, 0<c<1.5, 0<d<1

However, ripple is seen in the transmission wavelength band in FIG. 19.The film thickness was optimized in order to reduce the ripple andadjust the wavelength band. S-LAH55 (product name) manufactured by OHARAInc. (the material thereof having a refractive index 1.84 at awavelength of 550 nm) was used for the incident-side prism 11, TiO₂(with a refractive index of 2.32 at a wavelength of 550 nm) was used forthe H layer, MgF₂ (with a refractive index of 1.39 at a wavelength of550 nm) was used for the L layer, Al₂O₃ (with a refractive index 1.65 ata wavelength of 550 nm) was used for the M layer, and an adhesive with arefractive index of 1.55 was used on the emergence side. The number oflayers is 40 in total. Table 13 shows the thickness of each film. FIG.20 shows the transmittance at an incident angle of 45 degrees. Thenumber of a layer in Table 13 represents the order from the incidentside. At an incident angle of 45 degrees, s-polarized light istransmitted and p-polarized light is reflected in the blue wavelengthband (generally 430 to 490 nm), and s-polarized light is reflected andp-polarized light is transmitted in the red wavelength band (generally580 to 650 nm). Thus, it can be seen that favorable characteristics areprovided both in the separation of the wavelength bands and theexcellent polarization splitting.

EXAMPLE 12

Examples 2 to 7 have shown that the second multilayer film can berealized by laminating the three kinds of thin films, that is, the Hlayer with high refractive index, the L layer with low refractive index,the M layer with medium refractive index between those of the H and Llayers in the order of L, H, M, and H, and then adjusting the refractiveindex and film thickness. In addition, Examples 8 to 10 have shown thatthe fifth multilayer film similar to the second multilayer film can berealized by laminating the M layer, L layer, M layer, and H layer in theorder and then adjusting the refractive index and film thickness.

The present inventors have studied the second or fifth multilayer filmand found that three kinds of thin films, that is, an H layer with highrefractive index, an L layer with low refractive index, an M layer withmedium refractive index between those of the H and L layers arelaminated in the order of the L layer, M layer, L layer, and H layer,and the refractive index and film thickness are adjusted to provide aseventh multilayer film which can realize the similar characteristics tothose of the second or fifth multilayer film.

The seventh multilayer film is a multilayer of the L, M, L, and Hlayers, and has the optical characteristic of high transmittance ofs-polarized light in a first wavelength band, low transmittance ofp-polarized light in the first wavelength band, and high transmittancein a second wavelength band different from the first wavelength band.Each of the first wavelength band and the second wavelength band has abandwidth of 30 nm or more and includes a band in which the differencein transmittance is 60% or higher between s-polarized light ands-polarized light.

S-LAH55 (product name) manufactured by OHARA Inc. was used for anincident-side prism 11 and the material thereof has a refractive index1.84, the H layer (the material of the H layer) has a refractive indexof 2.32, the L layer (the material of the L layer) has a refractiveindex of 1.39, the M layer (the material of the M layer) has arefractive index of 1.65, and an adhesive with a refractive index of1.55 was used on the emergence side to bond two prisms. FIG. 21 showsthe wavelength characteristic of the transmittance of s-polarized lightand p-polarized light at an incident angle of 45 degrees in the filmstructure expressed as Prism|(0.5L1.9M0.5L0.32H)¹⁰|Adhesive at awavelength of 550 nm.

Similarly to FIG. 6 in Example 2 and FIG. 15 in Example 8, it basicallyshows the characteristic of an edge filter in which a transmission bandand a reflection band alternately appear, and it is characterized bysignificant polarization splitting in s-polarized light and p-polarizedlight. The significant polarization splitting can be used to provide thecharacteristic of transmitting s-polarized light and reflectingp-polarized light generally in the blue wavelength band (the firstwavelength band) and transmitting s-polarized light and p-polarizedlight in the red wavelength band (the second wavelength band), that is,provide the basic characteristic of the seventh multilayer film.

When multilayer films with shifted design wavelengths are laminated forthe seventh multilayer film, s-polarized light is hardly affected(although ripple is increased) since it is transmitted throughout thewavelength band (approximately 420 nm to 650 nm), and only the blockingwavelength band of p-polarized light is widened. Thus, the seventhmultilayer film can be put on another multilayer film to reduce only thetransmittance of p-polarized light in the blue wavelength band as awhole.

As a result, the first or sixth multilayer film can be put on theseventh multilayer film to provide a polarization beam splitter with anexcellent angular characteristic.

The result of study has shown that the polarization beam splitter can beprovided with an excellent angular characteristic by satisfying thefollowing relationship for the basic film structure in the sevenmultilayer film and appropriately selecting the refractive index andfilm thickness of each layer:(a×L b×M c×L d×H)0<d≦a≦b<5, 0<d≦c≦b<5where a, b, c, and d are real numbers, H the symbol for representing thequarter wavelength thickness of the layer with high refractive index ofd_(H)=/λ(4n_(H)), L the symbol for representing the quarter wavelengththickness of the layer with low refractive index of d_(L)=/λ(4n_(L)), Mthe symbol for representing the quarter wavelength thickness of thelayer with middle refractive index of d_(M)=/λ(4n_(M)), nH, nL, and nMthe refractive indexes of the H layer, L layer, and M layer,respectively, d_(H), d_(L), and d_(M) the film thickness of the H layer,L layer, and M layer, and λ the design wavelength.

In addition, the polarization beam splitter can be provided with a moreexcellent angular characteristic by satisfying the following therelationship for the basic film structure in the multilayer structureand appropriately selecting the refractive index and film thickness ofeach layer:(a×L b×M c×L d×H)0<d≦a≦b<3, 0<d≦c≦b<3

In specific design, the sixth multilayer film was put on the seventhmultilayer film including an increased number of layers for widening theblocking band at a small incident angle, and the thickness was optimizedin order to reduce ripple and adjust the wavelength band.

S-LAH55 (product name) manufactured by OHARA Inc. (with a refractiveindex 1.84 at a wavelength of 550 nm) was used for the incident-sideprism, TiO₂ (with a refractive index of 2.32 at a wavelength of 550 nm)was used for the H layer, MgF₂ (with a refractive index of 1.39 at awavelength of 550 nm) was used for the L layer, Al₂O₃ (with a refractiveindex 1.65 at a wavelength of 550 nm) was used for the M layer, and anadhesive with a refractive index of 1.55 was used on the emergence side.The number of layers is 100 in total. Table 14 shows the thickness ofeach film. FIG. 22 shows the transmittance at an incident angle of 45±2degrees. In the angular range of 45±2 degrees, s-polarized light istransmitted and p-polarized light is reflected in the blue wavelengthband, and s-polarized light is reflected and p-polarized light istransmitted in the red wavelength band, which shows favorablecharacteristics provided both in the separation of the wavelength bandsand the excellent polarization splitting.

It is obvious that the equivalent characteristics can also be achievedby putting the seventh multilayer film on the second multilayer filmhaving the similar characteristics to those of the sixth multilayerfilm, and the present invention is not limited thereto.

EXAMPLE 13

In Example 12, the three kinds of thin films, that is, the H layer withhigh refractive index, the L layer with low refractive index, the Mlayer with medium refractive index between those of the H and L layersare laminated in the order of the L layer, M layer, L layer, and Hlayer, and then the refractive index and film thickness are adjusted toprovide the seventh multilayer film. The seventh multilayer film is puton the sixth multilayer film. A polarization beam splitter in Example 13is formed by putting the third multilayer film on the seventh multilayerfilm provided by laminating the L layer, M layer, L layer, and H layer.

The third multilayer film has the optical characteristic of hightransmittance of s-polarized light in the first wavelength band, lowtransmittance in the second wavelength band, and high transmittance ofp-polarized light in the second wavelength band.

In specific design, the number of layers was increased to widen theblocking band in the seventh multilayer film, and the film thickness wasoptimized to reduce ripple and adjust the wavelength band. S-LAH55(product name) manufactured by OHARA Inc. (with a refractive index 1.84at a wavelength of 550 nm) was used for an incident-side prism 11, TiO₂(with a refractive index of 2.32 at a wavelength of 550 nm) was used forthe H layer, MgF₂ (with a refractive index of 1.39 at a wavelength of550 nm) was used for the L layer, Al₂O₃ (with a refractive index 1.65 ata wavelength of 550 nm) was used for the M layer, and an adhesive with arefractive index of 1.55 was used on the emergence side. The number oflayers is 117 in total. Table 15 shows the thickness of each film. FIG.23 shows the transmittance at an incident angle of 45±2 degrees. In theangular range of 45±2 degrees, s-polarized light is transmitted andp-polarized light is reflected in the blue wavelength band, ands-polarized light is reflected and p-polarized light is transmitted inthe red wavelength band, which shows favorable characteristics providedboth in the separation of the wavelength bands and the excellentpolarization splitting.

EXAMPLE 14

FIG. 24 is a schematic diagram showing the main portions of Example 14of a projection apparatus which employs the polarization beam splitterin any of Examples 1 to 13 of the present invention. FIG. 24 shows thestructure in which the wavelength selective polarization beam splitteris used as a color separation/combination means, a plurality ofreflection type liquid crystal display devices 55 b, 55 g, and 55 r areused to modulate polarization directions in accordance with a pluralityof signals, and a projection optical system 57 is used to project imagesproduced by the liquid crystal display devices.

Arrows represent the optical paths of respective light beams for red,green, and blue in white display (image information is for white color).Solid lines represent s-polarized light, while broken lines representp-polarized light.

Specifically, reference numerals 20 and 21 show s-polarized light andp-polarized light in the blue wavelength band, 30 and 31 s-polarizedlight and p-polarized light in the green wavelength band, and 40 and 41s-polarized light and p-polarized light in the red wavelength band.

White light 20, 30, and 40 emit from a light source 51 (a light sourcemeans) and are unified into s-polarized light by a polarization changer52. A dichroic mirror 53 a transmits the light beam 30 in the greenwavelength band (at wavelengths of approximately 500 to 580 nm), andreflects the light beam 40 in the red wavelength band (at wavelengths ofapproximately 580 to 650 nm) and the light beam 20 in the bluewavelength band (at wavelength of approximately 430 to 490 nm).

The light beam 30 in the green wavelength band transmitted through thedichroic mirror 53 a is reflected by a PBS 54 a, incident on areflection type liquid crystal display device 55 g for green, andmodulated. For the white display, the modulated light emerges therefromas p-polarized light 31 which is then transmitted through the PBS 54 aand a PBS 54 c and is incident on a projection lens system 57 forprojection.

The light beam 20 in the blue wavelength band reflected by the dichroicmirror 53 a is transmitted through a wavelength selective polarizationbeam splitter 1, incident on a reflection type liquid crystal displaydevice 55 b for blue, and modulated. For the white display, themodulated light emerges therefrom as p-polarized light 21, so that it isreflected by the wavelength selective polarization beam splitter 1 andchanged into s-polarized light 20 through a half-wave plate 58. It isthen reflected by the PBS 54 c and is incident on the projection lenssystem 57 for projection.

The light beam 40 in the red wavelength band reflected by the dichroicmirror 53 a is reflected by the wavelength selective polarization beamsplitter 1, incident on a reflection type liquid crystal display device55 r for red, and modulated. For the white display, since the modulatedlight emerges therefrom as p-polarized light 41, it is transmittedthrough the wavelength selective polarization beam splitter 1, changedinto s-polarized light 40 through the half-wave plate 58, reflected bythe PBS 54 c, and incident on the projection lens system 57 forprojection.

For black display (image information is for black color), all of thelight beams emerge from the reflection type liquid crystal displaydevices 55 r, 55 g, or 55 b with the same polarization as when they areincident thereon, so that they return toward the light source 51 alongthe same optical paths through the respective optical members. Thehalf-wave plate 58 preferably has no wavelength dependency.

The wavelength selective polarization beam splitter 1 replaces the PBS54b in the conventional liquid crystal projection optical system whichemploys the reflection type liquid crystal display device in FIG. 27 toeliminate the need to use the two wavelength selective phase shifters 56b and 56 r.

Since the wavelength selective polarization beam splitter in each ofExamples 1 to 13 is formed with a dielectric thin film which can befabricated through vacuum deposition or the like, the problemsassociated with the wavelength selective polarization beam splitter areimproved, and it is possible to realize a color separation/combinationmeans which achieves enhanced reliability and durability as well as highsurface accuracy in a simplified structure. In addition, the eliminationof wavelength selective phase shifters can increase the transmittance asa whole and the amount of projected light.

The color separation/combination means in FIG. 24 is only an example.Even when the optical members, wavelength bands for color separation,directions of light beams and the like are different from those in FIG.24, a projection apparatus can be realized by using the wavelengthselective polarization beam splitter. Particularly, the polarizerarranged between the components can block specific polarized light andreduce light leaked from the components, which is effective inimprovement of contrast. While the polarization changer 52 changes thelight into s-polarized light in FIG. 24, a similar projection apparatuscan also be provided by using p-polarized light, and the presentinvention is not limited thereto.

Since each prism in the color separation/combination system involves aphase difference due to stress associated with a temperature rise, thepolarization state of propagated light is changed. It is thus preferableto use an optical member with a low photoelastic constant. For example,PBH56 manufactured by OHRA Inc. with a photoelastic constant as low as0.09×10⁻⁸ cm²/N is preferably used. It is also preferable to use anoptical member in which the occurrence of stress is reduced. Since thestress is calculated by the function of the Young's modulus andexpansion coefficient, an optical member with a low Young's modulus anda low expansion coefficient is preferably used. For example, S-LAL14,S-LAH55 manufactured by OHARA Inc. or the like is preferably used.

When the manufacturing tolerance of the illumination optical system andcomponents, the spectral distribution of the light source means and thelike are considered in the characteristic of the wavelength selectivepolarization beam splitter in each of Examples 1 to 13, sufficientbrightness and contrast cannot be provided in the projection apparatusunless each of the first wavelength band and second wavelength band hasa bandwidth of 30 nm or more and the difference in transmittance is 60%or higher between s-polarized light and s-polarized light in the firstwavelength band and second wavelength band each having a bandwidth of 30nm or more. More preferably, each of the first wavelength band andsecond wavelength band has a bandwidth of 50 nm or more and thedifference in transmittance is 75% or higher between s-polarized lightand s-polarized light in the first wavelength band and second wavelengthband each having a bandwidth of 50 nm or more. It is apparent that alarger bandwidth and a greater difference in transmittance betweens-polarized light and p-polarized light are preferable. Design may bemade in view of that point.

The foregoing explanation applies to each of Examples described below.

EXAMPLE 15

FIG. 25 is a schematic diagram showing the main portions of a projectionapparatus of Example 15 of the present invention. Example 15 is theprojection apparatus which employs the wavelength selective polarizationbeam splitter in any of Examples 1 to 13 and a reflection type liquidcrystal display device, similarly to Example 14. In FIG. 25, arrowsrepresent the optical paths of respective light beams for red, green,and blue in white display. Solid lines represent s-polarized light,while broken lines represent p-polarized light.

White light 20, 30, and 40 emit from a light source 51 (a light sourcemeans) and are unified into s-polarized light by a polarization changer52. A dichroic mirror 53 a transmits the light beam 30 in the greenwavelength band, and reflects the light beam 40 in the red wavelengthband and the light beam 20 in the blue wavelength band. The light beam30 transmitted through the dichroic mirror 53 a is reflected by a PBS 54a, incident on a reflection type liquid crystal display device 55 grealized with liquid crystal for green, and modulated.

For the white display, the modulated light emerges therefrom asp-polarized light 31 which is then transmitted through the PBS 54 a anda dichroic prism 53 b, and incident on a projection lens system 57 forprojection. The dichroic prism 53 b is a device formed of prismssandwiching a multilayer film which transmits p-polarized light in thegreen wavelength band and reflects p-polarized light in the blue and redwavelength bands.

The light beam 20 in the blue wavelength band reflected by the dichroicmirror 53 a is transmitted through a wavelength selective polarizationbeam splitter 1, incident on a reflection type liquid crystal displaydevice 55 b for blue, and modulated. For the white display, themodulated light emerges therefrom as p-polarized light 21, so that it isreflected by the wavelength selective polarization beam splitter 1,reflected by the dichroic prism 53 b, and incident on the projectionlens system 57 for projection. The light beam 40 in the red wavelengthband reflected by the dichroic mirror 53 a is reflected by thewavelength selective polarization beam splitter 1, incident on areflection type liquid crystal display device 55 r for red, andmodulated. For the white display, since the modulated light emergestherefrom as p-polarized light 41, it is transmitted through thewavelength selective polarization beam splitter 1, reflected by thedichroic prism 53 b, and incident on the projection lens system 57 forprojection.

For black display, all of the light beams emerge from the reflectiontype liquid crystal display devices 55 r, 55 g, or 55 b with the samepolarization as when they are incident thereon, so that they returntoward the light source 51 along the same optical paths through therespective optical members.

Since Example 15 does not employ a half-wave plate, the transmittance isincreased as a whole and the amount of light is increased. Thewavelength selective polarization beam splitter 1 replaces the PBS 54 bin the conventional projection apparatus which employs the reflectiontype liquid crystal display device in FIG. 27 to eliminate the need touse the two wavelength selective phase shifters 56 b and 56 r. Since thewavelength selective polarization beam splitter in each of Examples 1 to13 is formed with a dielectric thin film which can be fabricated throughvacuum deposition or the like, the problems associated with thewavelength selective polarization beam splitter are improved, and it ispossible to realize a color separation/combination means which achievesenhanced reliability and durability as well as high surface accuracy ina simplified structure. In addition, the elimination of wavelengthselective phase shifters can increase the transmittance as a whole andthe amount of projected light.

EXAMPLE 16

FIG. 26 is a schematic diagram showing the main portions of a projectionapparatus of Example 16 of the present invention. Example 16 is providedto more enhance contrast and reduce flare in the projection apparatus ofExample 15.

In FIG. 25, solid lines represent s-polarized light, broken linesrepresent p-polarized light, and dashed lines represent circularlypolarized light.

Example 16 differs from Example 15 in that a polarizer 59 for blockings-polarized light is disposed between a PBS 54 a and a dichroic prism 53b and between a wavelength selective polarization beam splitter 1 andthe dichroic prism 53 b, and a quarter-wave plate 60 is disposed betweenthe dichroic prism 53 b and a projection lens system 57.

Since the polarizers 59 block light leaked from the PBS 54 a and thewavelength selective polarization beam splitter 1, contrast is improved.In particular, it can block leakage of s-polarized light reflected by areflection type liquid crystal display device from the PBS 54 a and thewavelength selective polarization beam splitter 1 in black display.Depending on an anti-reflection film, each lens of the projection lenssystem 57 reflects some amount of light, and the reflected light returnstoward the color separation/combination means as return light.

In the conventional color separation/combination means of FIG. 27, thereturn light reaches the light modulator realized with liquid crystaland thus causes flare. In contrast, in Example 16, the light beamsemerging from the quarter-wave plate 60 are circularly polarized light22, 32, and 42 in the blue, green, and red wavelength bands,respectively, and incident on the projection lens 57 for projection, asshown in FIG. 26(a). Return light 22, 32, and 42 from the projectionlens 57 are changed into s-polarized light 20, 30, and 40 through thequarter-wave plate 60, as show in FIG. 26(b). The dichroic prism 53 btransmits or reflects the light, but all of the transmitted light andreflected light are blocked by the polarizer 59.

Since the return light does not reach the light modulator realized withliquid crystal, the flare can be reduced. The colorseparation/combination means in FIGS. 26(a) and 26(b) is only anexample. Even when the optical members, wavelength bands for colorseparation, directions of light beams and the like are different fromthose in FIG. 26, a projection apparatus can be realized by using thewavelength selective polarization beam splitter.

As described above, the projection apparatus of each of Examples has thelight source means, the polarization changing means for unifying thepolarization directions of non-polarized light, the means forseparating/combining light depending on the wavelength band, the opticalmeans for having both of the functions of color separation andcombination of light with any one of the polarization beam splitters inExamples 1 to 13, the light modulating means for modulating thepolarization direction, and the projection means for projecting thecombined light.

The projection apparatus (the image display apparatus) of each ofExamples has the plurality of reflection type liquid crystal displaydevices (reflection type liquid crystal panels), and the optical memberwhich illuminates the plurality of reflection type liquid crystaldisplay devices with light for a plurality of colors, and combines andprojects the light for the plurality of colors from the plurality ofreflection type liquid crystal display devices. The optical systememploys the polarization beam splitter described in any one of Examples1 to 13 to combine the light for the plurality of colors from theplurality of reflection type liquid crystal display devices. The opticalsystem has an optical axis at an angle of approximately 45 degrees (anangle in the range of 44 to 46 degrees) with respect to the multilayerfilm (the surface on which the multilayer film structure is formed) ofthe polarization beam splitter. A light beam incident on the multilayerfilm of the polarization beam splitter has the range of incident anglesequal to or smaller than 10 degrees (in other words, the light beam isincident on the surface on which the multilayer film structure is formedat an angle in the range of 40 to 50 degrees).

As described above, according to each of Examples, the polarization beamsplitter with wavelength selectivity including the laminated thin filmshaving three different refractive indexes (three ranges of refractiveindexes different from one another) can be used to realize the opticalsystem (the projection apparatus) with no need for a wavelengthselective phase changer in a color separation/combination means in anoptical system of a reflection type liquid crystal projector, whichenables the optical system with small size and high durability. Inaddition, it is possible to realize the structure of the colorseparation/combination means which blocks return light reflected by theprojection lens to provide an optical system which allows improvedcontrast and reduced flare.

Examples discussed above will be described with reference to Table 16.Table 16 shows the general structure of the main components of themultilayer film (the general structure of the multilayer film) used inthe polarization beam splitter of Examples 1 to 13, the material and therefractive index of the incident-side prism, the refractive index of thehigh refractive index layer, the refractive index of the middlerefractive index layer, the refractive index of the low refractive indexlayer, the refractive index of the adhesive disposed on the emergenceside, the difference in refractive index between the high refractiveindex layer and the middle refractive index layer, the difference inrefractive index between the middle refractive index layer and the lowrefractive index layer, the transmittance (%) of p-polarized light at awavelength of 430 nm, the transmittance (%) of s-polarized light at awavelength of 430 nm, the difference (%) in transmittance betweens-polarized light and p-polarized light at a wavelength of 430 nm, thetransmittance (%) of p-polarized light at a wavelength of 490 nm, thetransmittance (%) of s-polarized light at a wavelength of 490 nm, thedifference (%) in transmittance between s-polarized light andp-polarized light at a wavelength of 490 nm, the transmittance (%) ofp-polarized light at a wavelength of 580 nm, the transmittance (%) ofs-polarized light at a wavelength of 580 nm, the difference (%) intransmittance between s-polarized light and p-polarized light at awavelength of 580 nm, the transmittance (%) of p-polarized light at awavelength of 650 nm, the transmittance (%) of s-polarized light at awavelength of 650 nm, and the difference (%) in transmittance betweens-polarized light and p-polarized light at a wavelength of 650 nm.

The wavelengths of 430 nm and 490 nm correspond to the region in whichthe polarization beam splitters of Examples 1 to 3 and Examples 5 to 13transmit s-polarized light and reflect p-polarized light (that is, thefirst wavelength band). In Example 4, the wavelengths correspond toapproximate upper and lower limits (variations of approximately 10 to 20nm are present in some of Examples) of the region in which s-polarizedlight is reflected and p-polarized light is transmitted (that is, thesecond wavelength band).

The wavelengths of 580 nm and 650 nm correspond to the region in whichthe polarization beam splitters of Examples 1 to 3 and Examples 5 to 13transmit p-polarized light and reflect s-polarized light (that is, thesecond wavelength band). In Example 4, the wavelengths correspond toapproximate upper and lower limits (variations of approximately 10 to 20nm are present in some of Examples) of the region in which p-polarizedlight is reflected and s-polarized light is transmitted (that is, thefirst wavelength band).

While the difference in transmittance is shown, the difference intransmittance between p-polarized light and s-polarized light in therange of a wavelength of 430 nm to a wavelength of 490 nm is equal to orlarger than the difference in transmittance at a wavelength of 430 nmand the difference in transmittance at a wavelength of 490 nm. The sameapplies to the range of a wavelength of 580 nm to a wavelength of 650nm.

The following can be seen from Table 16. The following description showsconditions which are satisfied in at least some of Examples as apparentfrom Table 16.

It is desirable that the prism (a different optical member may be usedas long as it is a transmission type member) disposed on the incidentside has a refractive index of 1.55 (preferably 1.65) or hither and 2.1(preferably 1.90) or lower.

The high refractive index layer desirably has a refractive index of 2.0(preferably 2.1) or higher and 2.6 (preferably 2.35) or lower.

The middle refractive index layer desirably has a refractive index of1.59 (preferably 1.60) or higher and 1.9 (preferably 1.82) or lower.

The low refractive index layer desirably has a refractive index of 1.25(preferably 1.35) or higher and 1.56 (preferably 1.50) or lower.

The adhesive on the emergence side desirably has a refractive index of1.40 (preferably 1.50) or higher and 1.70 (preferably 1.60) or lower.

The difference in transmittance between the high refractive index layerand the middle refractive index layer is desirably 0.35 (preferably0.48) or higher and 0.9 (preferably 0.70) or lower.

The difference in transmittance between the middle refractive indexlayer and the low refractive index layer is desirably 0.12 (preferably0.15) or higher and 0.55 (preferably 0.42) or lower.

The first wavelength range desirably includes a region of at least 450to 480 nm (preferably 430 nm to 490 nm). It may include a region of 600to 630 nm (preferably 585 to 630 nm) as in Example 4. In the firstwavelength region, s-polarized light desirably has a transmittance of60% (more preferably 80%, and even more preferably 90%) or higher, andp-polarized light desirably has a transmittance of 40% (more preferably32%, and even more preferably 20%) or lower. As a result, the differencein transmittance between s-polarized light and p-polarized light is 60%(more preferably 70%, and even more desirably 80%) or higher. In Example4, s-polarized light desirably has a transmittance of 40% (moredesirably 30%, and more preferably 20%) or lower, and p-polarized lightdesirably has a transmittance of 60% (more desirably 80%, and morepreferably 90%) or higher. As a result, in Example 4, the difference intransmittance between s-polarized light and p-polarized light is 60%(more preferably 70%) or higher.

The second wavelength range desirably includes a wavelength region of atleast 600 to 630 nm (preferably 590 nm to 650 nm). It may include aregion of 450 to 480 nm (preferably 430 to 490 nm) as in Example 4. Inthe second wavelength region, s-polarized light desirably has atransmittance of 40% (preferably 20%, and more desirably 10%) or lower,and p-polarized light desirably has a transmittance of 60% (preferably80%, and more preferably 90%) or higher. As a result, the difference intransmittance between s-polarized light and p-polarized light is 60%(preferably 70%, and more preferably 75%) or higher. In Example 4,s-polarized light desirably has a transmittance of 40% (preferably 15%,and more preferably 7%) or lower, and p-polarized light desirably has atransmittance of 60% (preferably 70%) or higher. As a result, in Example4, the difference in transmittance between s-polarized light andp-polarized light is 60% (preferably 70%, and more preferably 72%) orhigher.

From the foregoing explanation, the following can be seen in all ofExamples.

The polarization beam splitter described in each of the Examplesincludes a multilayer film formed by laminating a first layer having arefractive index in a first range, a second layer having a refractiveindex in a second range which does not overlap the first range, and athird layer having a refractive index in a third range which does notoverlap the first or second range in the order of the first layer, thesecond layer, the first layer, and the third layer in succession. Thepolarization beam splitter has transmittance of s-polarized light is 60%or more higher than the transmittance of p-polarized light in a firstwavelength region and has transmittance of p-polarized light equal to orhigher than 70% in a second wavelength band different from the firstwavelength band. Each of the first wavelength region and the secondwavelength region has a bandwidth equal to or larger than 30 nm.Alternatively, the polarization beam splitter has transmittance ofs-polarized light 60% or more higher than the transmittance ofp-polarized light in a first wavelength region and has transmittance ofp-polarized light 60% or more higher than the transmittance ofs-polarized light in a second wavelength band different from the firstwavelength band. Each of the first wavelength region and the secondwavelength region has a bandwidth equal to or larger than 30 nm. Themultilayer film is a multilayer film formed by laminating the firstlayer, the second layer, the first layer, and the third layer in thisorder in succession five times or more (preferably ten times).

The first wavelength region and the second wavelength region areincluded in region of visible wavelength (400 nm or higher and 700 nm orlower). The first wavelength region includes a band of 450 nm to 480 nmand the second wavelength region includes a band of 600 nm to 630 nm.

When a layer of the first, second, and third layers with the highestrefractive index is an H layer (a high refractive index layer), a layerof the three layers with the second highest refractive index is an Mlayer (a middle refractive index layer), and a layer of the three layerswith the lowest refractive index is an L layer (a low refractive indexlayer), then the high refractive index layer has a refractive index of2.0 or higher and 2.6 or lower, the middle refractive index layer has arefractive index of 1.59 or higher and 1.9 or lower, and the lowrefractive index layer has a refractive index of 1.25 or higher and 1.56or lower.

When a layer of the first, second, and third layers with the highestrefractive index is an H layer (a high refractive index layer), a layerof the three layers with the second highest refractive index is an Mlayer (a middle refractive index layer), and a layer of the three layerswith the lowest refractive index is an L layer (a low refractive indexlayer), then the difference in the refractive index between the highrefractive index layer and the middle refractive index layer is 0.35 orhigher and 0.9 or lower, and the difference in the refractive indexbetween the middle refractive index layer and the lower refractive indexlayer is 0.12 or higher and 0.55 or lower. The multilayer film issandwiched between a substance made of a first material having arefractive index of 1.55 or higher and 2.10 or lower and a substancemade of a second material having a refractive index of 1.40 or higherand 1.70 or lower. At least one of the first layer, the second layer,and the third layer includes two layers having refractive indexesdifferent from each other (Example 5 shows the example in which twokinds of materials are used as the material for the middle refractiveindex layer and two kinds of materials are used as the material for thelow refractive index layer, but naturally it is contemplated that twokinds of materials are used as materials for the high refractive indexlayer).

The following can be seen in Examples 1 to 7.

The first range corresponds to the highest range of refractive indexesof the first, second, and third ranges. When a layer of the first,second, and third layers with the highest refractive index is an Hlayer, a layer of the three layers with the second highest refractiveindex is an M layer, a layer of the three layers with the lowestrefractive index is an L layer, the refractive indexes of the H layer, Llayer, and M layer are represented as n_(H), n_(L), and n_(M), a designwavelength is represented as λ, the multilayer film is formed bylaminating the first H layer, the M layer, the second H layer, and the Llayer in this order in succession, and the film thickness of the first Hlayer, the M layer, the second H layer, and the L layer are representedas b×λ/(4n_(H)), c×λ/(4n_(M)), d×λ/(4n_(H)), a×λ/(4n_(L)), then 0<a<3,0<b≦1, 0<c<5, and 0<d≦1 are satisfied. More desirably, 0<b≦a≦c<5,0<d≦a≦c<5 are satisfied.

The following can be seen in Examples 8 to 10.

The first range corresponds to the second highest range of refractiveindexes of the first, second, and third ranges. When a layer of thefirst, second, and third layers with the highest refractive index is anH layer, a layer of the three layers with the second highest refractiveindex is an M layer, a layer of the three layers with the lowestrefractive index is an L layer, the refractive indexes of the H layer, Llayer, and M layer are represented as n_(H), n_(L), and n_(M), a designwavelength is represented as λ, the multilayer film is formed bylaminating the first M layer, the L layer, the second M layer, and the Hlayer in this order in succession, and the film thickness of the first Mlayer, the L layer, the second M layer, and the H layer are representedas a×λ/(4n_(M)), b×λ/(4n_(L)), c×λ/(4n_(M)) d×λ/(4n_(H)), then 0<a<6,0<c<6, d<b, 0<b<5, and 0<d<2 are satisfied. More desirably, 0<a<3,0<c<6, d<b, 0<b<2, and 0<d<1 are satisfied.

The following can be seen in Examples 11 to 13.

The first range corresponds to the lowest range of refractive indexes ofthe first, second, and third ranges. When a layer of the first, second,and third layers with the highest refractive index is an H layer, alayer of the three layers with the second highest refractive index is anM layer, a layer of the three layers with the lowest refractive index isan L layer, the refractive indexes of the H layer, L layer, and M layerare represented as n_(H), n_(L), and n_(M), a design wavelength isrepresented as λ, the multilayer film is formed by laminating the firstL layer, the H layer, the second L layer, and the M layer in this orderin succession, and the film thickness of the first L layer, the H layer,the second L layer, and the M layer are represented as a×λ/(4n_(L)),b×λ/(4n_(H)), c×λ/(4n_(L)), d×λ/(4n_(M)), then 0<a<3, 0<b<5, d<b, 0<c<3,and 0<d<1 are satisfied. More desirably, 0<b≦a≦c<5, 0<d≦a≦c<5 aresatisfied.

The following can be seen in Example 14 to 16. The image displayapparatus described in Examples 14 to 16 includes a first image displaydevice, a second image display device, and a color combination opticalsystem which combines first image light emerging from the first imagedisplay device and second image light emerging from the second imagedisplay device, wherein the color combination optical system has thepolarization beam splitter as described above. The image displayapparatus described in Examples 14 to 16 includes a first reflectiontype liquid crystal display device which is provided for first colorlight, a second reflection type liquid crystal display device which isprovided for second color light different from the first color light, anillumination optical system which illuminates the first and secondreflection type liquid crystal display devices with light from a lightsource, and a projection optical system which projects light from thefirst and second reflection type liquid crystal display devices to aprojected surface, wherein the illumination optical system includes thepolarization beam splitter as described above, and the first color lightin a first polarization state and the second color light in the firstpolarization state are directed to the polarization beam splitter toilluminate the first reflection type liquid crystal display device withthe first color light in the first polarization state and illuminate thesecond reflection type liquid crystal display device with the secondcolor light in the first polarization state, and the polarization beamsplitter color-combines the first color light in a second polarizationstate and the second color light in the second polarization stateemerging from the first reflection type liquid crystal display deviceand the second reflection type liquid crystal display device,respectively, to direct the combined light to the projection opticalsystem, the second polarization state showing a polarization directionorthogonal to the first polarization state.

According to Examples as described above, it is possible to provide thepolarization beam splitter which can transmits s-polarized light andreflects p-polarized light in a wavelength band and the image displayapparatus which employs the polarization beam splitter.

This application claims a foreign priority based on Japanese PatentApplications Nos. 2004-232126, filed on Aug. 9, 2004 and 2005-149943,filed on May 23, 2005, and each of which is hereby incorporated byreference herein. TABLE 1 EXAMPLE 1 PRISM PBH56 H LAYER TiO₂ M LAYERAl₂O₃ L LAYER MgF₂ INCIDENT ANGLE 45° FIRST WAVELENGTH BAND BLUE SECONDWAVELENGTH BAND RED LAYER NUMBER MATERIAL FILM THICKNESS 1 L 70.66 2 H26.45 3 M 96.53 4 H 39.69 5 L 73.55 6 H 7.03 7 M 110.43 8 H 1.21 9 L128.8 10 H 33.91 11 M 115.31 12 H 17.83 13 L 125.68 14 H 19.29 15 M96.21 16 H 9.82 17 L 116.6 18 H 27.68 19 M 95.48 20 H 22.62 21 L 143 22H 19.38 23 M 85.88 24 H 20.76 25 L 157.17 26 H 20.98 27 M 89.83 28 H31.88 29 L 131.78 30 H 10.57 31 M 70.79 32 H 28.64 33 L 86.91 34 H 20.8435 M 91.43 36 H 58.71 37 L 87.14 38 H 32.94 39 M 65.8 40 H 32.24(nm)

TABLE 2 EXAMPLE 2 PRISM PBH56 H LAYER TiO₂ M LAYER Al₂O₃ L LAYER MgF₂INCIDENT ANGLE 45 ± 5° FIRST BLUE WAVELENGTH BAND SECOND RED WAVELENGTHBAND LAYER FILM NUMBER MATERIAL THICKNESS 1 M 98.07 2 H 11.64 3 L 80.554 H 5.85 5 M 100.99 6 H 14.55 7 L 48.92 8 H 28.11 9 M 109.47 10 H 16.6111 L 67.84 12 H 14.17 13 M 98.6 14 H 9.33 15 L 74.44 16 H 15.36 17 M108.53 18 H 30.6 19 L 55.04 20 H 4.51 21 M 105.02 22 H 2.65 23 L 108.1324 H 7.73 25 M 104.17 26 H 9.78 27 L 50.06 28 H 25.43 29 M 104.79 30 H20.09 31 L 55.13 32 H 11.74 33 M 102.06 34 H 17.78 35 L 54.17 36 H 20.4237 M 105.54 38 H 15.36 39 L 69.55 40 H 18.18 41 M 100.25 42 H 16.38 43 L76.31 44 H 16.06 45 M 103.82 46 H 24.53 47 L 52.1 48 H 20.46 49 M 107.150 H 23.22 51 L 70.99 52 H 18.85 53 M 106.31 54 H 32.23 55 L 36.82 56 H23.06 57 M 121.08 58 H 12.66 59 L 54.6 60 H 28.3 61 M 116.73 62 H 11.3763 L 90.5 64 H 12.24 65 M 102.92 66 H 21.19 67 L 84.77 68 H 9.42 69 M120.63 70 H 17.9 71 L 1.63 72 H 56.71 73 M 103.1 74 H 14.82 75 L 71.4976 H 49.23 77 M 64.31 78 H 23.35 79 L 65.22 80 H 42.83 81 M 46.85 82 H37.6 83 L 88.62 84 H 48.53 85 M 37.15 86 H 50.67 87 L 79.89 88 H 49.6589 M 41.91 90 H 44.33 91 L 80.53 92 H 14.17 93 M 55.12 94 H 42.29 95 L73.09 96 H 41.35 97 M 51.74 98 H 47.16 99 L 69.62 100 H 45.99 101 M56.16 102 H 31.5 103 L 48.4(nm)

TABLE 3 THIRD MULTILAYER FILM PRISM PBH56 H LAYER TiO₂ M LAYER Al₂O₃ LLAYER SiO₂ INCIDENT ANGLE 45 ± 10° FIRST WAVELENGTH BAND BLUE SECONDWAVELENGTH BAND RED LAYER NUMBER MATERIAL FILM THICKNESS 1 M 39.79 2 H137.11 3 M 50.47 4 H 163.41 5 M 29.44 6 H 162.36 7 M 62.55 8 H 138.98 9M 57.83 10 H 365.65 11 L 39.41 12 H 137.1 13 L 48.67 14 H 127.82 15 L53.72 16 H 127.79 17 L 57.95 18 H 128.6 19 L 56.91 20 H 128.85 21 L33.15 22 H 126.05 23 L 48.29 24 H 124.59(nm)

TABLE 4 EXAMPLE 3 PRISM PBH56 H LAYER TiO₂ M LAYER Al₂O₃ L1 LAYER MgF₂L2 LAYER SiO₂ INCIDENT ANGLE 45 ± 5° FIRST BLUE WAVELENGTH BAND SECONDRED WAVELENGTH BAND LAYER FILM NUMBER MATERIAL THICKNESS 1 M 95.72 2 H21.2 3 L1 62.77 4 H 26.6 5 M 79.45 6 H 10.56 7 L1 87.12 8 H 19.03 9 M93.14 10 H 30.93 11 L1 45.95 12 H 9.14 13 M 103.78 14 H 14.36 15 L152.26 16 H 24.53 17 M 99.8 18 H 11.97 19 L1 73.22 20 H 9.9 21 M 93.84 22H 20.71 23 L1 71.91 24 H 9.55 25 M 107.98 26 H 3.17 27 L1 51.1 28 H32.97 29 M 107.51 30 H 12.8 31 L1 73.03 32 H 5.92 33 M 99.1 34 H 28.5635 L1 48.68 36 H 13.04 37 M 101.81 38 H 15.92 39 L1 50.99 40 H 30.02 41M 90.86 42 H 9.74 43 L1 91.99 44 H 21.79 45 M 80.73 46 H 34.34 47 L154.24 48 H 10.1 49 M 83.88 50 H 38.12 51 L1 44.81 52 H 26.51 53 M 83.1154 H 16.34 55 L1 39.09 56 H 39.93 57 M 81.79 58 H 27.12 59 L1 73.79 60 H47.11 61 M 46.85 62 H 28.07 63 L1 82.24 64 H 18.84 65 M 90.41 66 H 38.1267 L1 59.81 68 H 20.12 69 M 100.14 70 H 18.8 71 L1 54.9 72 H 17.95 73 M93.01 74 H 21.93 75 L1 43.01 76 H 26.72 77 M 105.85 78 H 20.88 79 L162.24 80 H 26.02 81 M 107.91 82 H 17.52 83 L1 68.35 84 H 31.1 85 M 94.7686 H 21.48 87 L1 98.77 88 H 25.2 89 M 94.58 90 H 27.23 91 L1 75.84 92 H18.07 93 M 100.88 94 H 25.12 95 L1 72.97 96 H 26.13 97 M 99.09 98 H40.53 99 L1 55.37 100 H 46.62 101 M 67.83 102 H 37.05 103 L1 63.28 104 H31.12 105 M 81.84 106 H 24 107 L1 87.2 108 H 27.49 109 M 78.02 110 H46.82 111 L1 60.23 112 H 32.86 113 M 103.68 114 H 16.61 115 L1 61.09 116H 15.29 117 M 85.42 118 H 43.7 119 L1 61.71 120 H 25.78 121 M 94.14 122H 168.76 123 M 21.53 124 H 172.12 125 M 31.43 126 H 163.63 127 M 40.79128 H 153.42 129 M 38.44 130 H 372.55 131 L2 43.49 132 H 139.26 133 L261.03 134 H 127.68 135 L2 39.58 136 H 127.58 137 L2 57.39 138 H 133.41139 L2 36.21 140 H 117.8 141 L2 43.05 142 H 133.93 143 L2 76.22 144 H122.91(nm)

TABLE 5 EXAMPLE 4 PRISM PBH56 H LAYER TiO₂ M1 LAYER Y₂O₃ M2 LAYER Al₂O₃L1 LAYER MgF₂ L2 LAYER SiO₂ INCIDENT ANGLE 45 ± 5° FIRST BLUE WAVELENGTHBAND SECOND RED WAVELENGTH BAND LAYER FILM NUMBER MATERIAL THICKNESS 1M1 138.67 2 H 29.45 3 L1 31.1 4 H 62.73 5 M1 132.91 6 H 21.02 7 L1 79.158 H 47.17 9 M1 123.51 10 H 34.82 11 L1 79.34 12 H 32.88 13 M1 113.61 14H 38.44 15 L1 38.34 16 H 44.42 17 M1 105.2 18 H 33.66 19 L1 80.92 20 H42.69 21 M1 118.74 22 H 45.28 23 L1 85.81 24 H 39.39 25 M1 144.29 26 H36.17 27 L1 81.29 28 H 42.2 29 M1 110.12 30 H 45.44 31 L1 52.31 32 H35.14 33 M1 115.93 34 H 28.22 35 L1 71.22 36 H 41.31 37 M1 127.07 38 H32.4 39 L1 107.43 40 H 26.79 41 M1 121.88 42 H 49.61 43 L1 58.96 44 H14.11 45 M1 115.79 46 H 36.59 47 L1 29.26 48 H 38.42 49 M1 116.1 50 H25.18 51 L1 41.5 52 H 42.76 53 M1 109.37 54 H 29.38 55 L1 50.48 56 H38.39 57 M1 111.92 58 H 30.38 59 L1 59.49 60 H 37.26 61 M1 111.76 62 H30.11 63 L1 63.99 64 H 32.79 65 M1 124.32 66 H 36.16 67 L1 85.18 68 H22.74 69 M1 127.93 70 H 45.35 71 L1 47.82 72 H 18.79 73 M1 116.23 74 H31.03 75 L1 22.01 76 H 45.72 77 M1 112.02 78 H 23.51 79 L1 59.64 80 H45.38 81 M1 97.14 82 H 36.48 83 L1 45.51 84 H 37.73 85 M1 87.38 86 H45.52 87 L1 47.24 88 H 40.79 89 M1 77.98 90 H 45.89 91 L1 42.53 92 H41.74 93 M1 78.21 94 H 44.49 95 L1 34.47 96 H 43.9 97 M1 74.47 98 H44.66 99 L1 40.2 100 H 48.08 101 M1 72.37 102 H 40.04 103 L1 33.08 104 H49.27 105 M1 72.49 106 H 45.87 107 L1 29.24 108 H 42.25 109 M1 68.74 110H 42.65 111 L1 32.47 112 H 45.24 113 M1 85.83 114 H 48.08 115 L1 24.74116 H 46.06 117 M1 68.4 118 H 51.7 119 L1 42.37 120 H 41.93 121 M1 63.55122 H 51.51 123 L1 39.87 124 H 48.2 125 M1 63.29 126 H 49.85 127 L1 35.9128 H 48.51 129 M1 69.12 130 H 44.84 131 L1 32.59 132 H 51.44 133 M173.5 134 H 28.75 135 L1 30.42 136 H 57.35 137 M1 84.55 138 H 39.45 139L1 70.57 140 H 16.82 141 M2 149.23 142 H 171.82 143 M2 162.87 144 H182.74 145 M2 94.18 146 H 222.84 147 M2 37.9 148 H 234.52 149 M2 28.03150 H 212.88

TABLE 6 LAYER NUMBER MATERIAL FILM THICKNESS 151 L2 12.1 152 H 275.76153 L2 3.4 154 H 178.35 155 L2 6.96 156 H 221.72 157 L2 24.71 158 H168.82 159 L2 22.04 160 H 209.66 161 L2 41.7 162 H 170.96 163 L2 40.29164 H 180.44(nm)

TABLE 7 EXAMPLE 5 PRISM PBH56 H LAYER TiO₂ M LAYER Y₂O₃ L LAYER SiO₂INCIDENT ANGLE 45 ± 5° FIRST BLUE WAVELENGTH BAND SECOND RED WAVELENGTHBAND LAYER FILM NUMBER MATERIAL THICKNESS 1 M 87.02 2 H 17.18 3 L 45.984 H 15.11 5 M 77.14 6 H 14.3 7 L 41 8 H 21.58 9 M 82.78 10 H 17.14 11 L39.87 12 H 18.59 13 M 83.95 14 H 19.26 15 L 34.27 16 H 19.15 17 M 83.918 H 18.65 19 L 40.42 20 H 17.32 21 M 84.15 22 H 20.5 23 L 38.52 24 H16.83 25 M 83.15 26 H 17.84 27 L 38.28 28 H 19.04 29 M 81.85 30 H 16.331 L 40.71 32 H 18.65 33 M 81.48 34 H 17.17 35 L 42.89 36 H 16.28 37 M79.37 38 H 19.56 39 L 32.32 40 H 17.35 41 M 79.25 42 H 14.65 43 L 36.2144 H 21.25 45 M 82.58 46 H 15.97 47 L 43.6 48 H 17.3 49 M 83.78 50 H20.34 51 L 36.73 52 H 16.98 53 M 83 54 H 20.1 55 L 37.82 56 H 17.53 57 M82.41 58 H 20.2 59 L 36.37 60 M 19.47 61 H 83.33 62 H 16.93 63 L 44.2764 H 20.52 65 M 84.53 66 H 18.67 67 L 44.2 68 H 19.53 69 M 85.62 70 H22.78 71 L 38.11 72 H 21.38 73 M 87.96 74 H 21.66 75 L 46.46 76 H 22.6377 M 88.31 78 H 22.13 79 L 46.15 80 H 20.41 81 M 86.25 82 H 23.83 83 L35.19 84 H 19.96 85 M 84.76 86 H 17.94 87 L 40.89 88 H 20.76 89 M 84.5390 H 18.96 91 L 40.66 92 H 18.7 93 M 84.9 94 H 18.89 95 L 97.01 96 H20.86 97 M 84.25 98 H 17.13 99 L 47.46 100 H 18.57 101 M 85.48 102 H23.74 103 L 42.12 104 H 18.93 105 M 87.32 106 H 25.12 107 L 38.11 108 H24.57 109 M 85.54 110 H 22.99 111 L 40.62 112 H 23.99 113 M 83.84 114 H23.59 115 L 36.6 116 H 22.69 117 M 84.68 118 H 21.22 119 L 39.38 120 H23.23 121 M 85.26 122 H 18.64 123 L 47.9 124 H 21.46 125 M 86.26 126 H20.94 127 L 43.2 128 H 21.4 129 M 91.61 130 H 20.65 131 L 50.97 132 H24.62 133 M 98.37 134 H 21.62 135 L 62.81 136 H 21.84 137 M 93.53 138 H20.87 139 L 56.71 140 H 18.15 141 M 95.49 142 H 26.42 143 L 52.68 144 H14.93 145 M 102.02 146 H 25.41 147 L 49.44 148 H 19.71 149 M 98.48 150 H27.04

TABLE 8 FILM LAYER NUMBER MATERIAL THICKNESS 151 L 34.99 152 H 19.71 153M 92.62 154 H 28.33 155 L 33.06 156 H 17.28 157 M 91.61 158 H 13.1 159 L47.09 160 H 26.06 161 M 93.63 162 H 16.97 163 L 48.68 164 H 23.74 165 M107.93 166 H 18.57 167 L 50.6 168 H 29.7 169 M 93.28 170 H 12.76 171 L83.45 172 H 27 173 M 81.39 174 H 27.43 175 L 76.99 176 H 39.35 177 M59.7 178 H 29.79 179 L 93.3 180 H 32.38 181 M 63 182 H 35.49 183 L 97.06184 H 41.83 185 M 39.85 186 H 46.93 187 L 91.07 188 H 33.42 189 M 47.32190 H 38.37 191 L 68.79 192 H 13.86 193 M 76.19 194 H 55.39 195 L 46.14196 H 8.98 197 M 80.98 198 H 112.43 199 L 31.7 200 H 78.78 201 M 64.72202 H 9.84 203 L 78.22(nm)

TABLE 9 EXAMPLE 6 PRISM S-LAL14 H LAYER TiO₂ M LAYER Al₂O₃ L LAYER MgF₂INCIDENT ANGLE 45 ± 5° FIRST BLUE WAVELENGTH BAND SECOND RED WAVELENGTHBAND LAYER FILM NUMBER MATERIAL THICKNESS 1 M 108.34 2 H 14.14 3 L 63.854 H 21.6 5 M 108.06 6 H 20.12 7 L 61.29 8 H 16.84 9 M 101.81 10 H 16.5411 L 63.38 12 H 18.71 13 M 101.28 14 H 21.98 15 L 52.64 18 H 18.72 17 M100.53 18 H 19.05 19 L 55.95 20 H 21.35 21 M 97.75 22 H 18.08 23 L 60.5324 H 19.24 25 M 96.12 26 H 21.07 27 L 56.12 28 H 19.03 29 M 95.37 30 H21.58 31 L 51.69 32 H 20.23 33 M 98.14 34 H 19.83 35 L 57.85 36 H 21.6637 M 101.62 38 H 23 39 L 58.61 40 H 20.5 41 M 98.8 42 H 23.88 43 L 49.7544 H 21.87 45 M 93.46 46 H 22.38 47 L 48.2 48 H 23.33 49 M 92.11 50 H21.29 51 L 51.97 52 H 23.17 53 M 93.05 54 H 20.72 55 L 52.87 56 H 22.3457 M 94.96 58 H 18.83 59 L 56.11 60 H 20.87 61 M 99.18 62 H 15.73 63 L65.61 64 H 17.43 65 M 102.5 66 H 16.23 67 L 63.02 68 H 14.74 69 M 103.7470 H 15.28 71 L 56.8 72 H 6.75 73 M 93.53 74 H 8.55 75 L 46.03 76 H11.57 77 M 101.12 78 H 11.41 79 L 52.74 80 H 21.04 81 M 100.74 82 H16.13 83 L 69 84 H 19.4 85 M 102.54 86 H 16.33 87 L 68.92 88 H 16.84 89M 98.8 90 H 17.74 91 L 63.22 92 H 15.32 93 M 94.7 94 H 19.55 95 L 58.4196 H 15.45 97 M 91.16 98 H 22.5 99 L 42.38 100 H 17.81 101 M 89.91 102 H15.61 103 L 42.13 104 H 17.95 105 M 92.54 106 H 10.24 107 L 58.92 108 H10.63 109 M 98.95 110 H 15.51 111 L 50.37 112 H 17.17 113 M 100.05 114 H12.2 115 L 71.41 116 H 11.17 117 M 101.35 118 H 26.24 119 L 46.29 120 H21.24 121 M 95.49 122 H 25.82 123 L 47.87 124 H 24.08 125 M 93.99 126 H18.18 127 L 58.03 128 H 15.7 129 M 92.77 130 H 21.1 131 L 41.38 132 H15.54 133 M 92.02 134 H 4.7 135 L 81.15 136 H 10.36 137 M 98.48 138 H15.28 139 L 49.76 140 H 15.52 141 M 96.97 142 H 18.06 143 L 54.14 144 H15.32 145 M 93.16 146 H 18.36 147 L 50.59 148 H 16.52 149 M 90.71 150 H18.05

TABLE 10 LAYER FILM NUMBER MATERIAL THICKNESS 151 L 42.69 152 H 16.82153 M 87.5 154 H 8.74 155 L 52.31 156 H 10.83 157 M 91.18 158 H 14.43159 L 49.95 160 H 14.31 161 M 92 162 H 18.91 163 L 53.05 164 H 14.19 165M 88.16 166 H 17.49 167 L 47.36 168 H 17.75 169 M 88.56 170 H 13.51 171L 41.98 172 H 19.8 173 M 93.58 174 H 6.76 175 L 67.27 176 H 7.23 177 M97.27 178 H 20.96 179 L 29.23 180 H 19.42 181 M 92.41 182 H 17.65 183 L59.87 184 H 14.67 185 M 89.89 186 H 20.22 187 L 40.78 188 H 20.95 189 M93.21 190 H 10.31 191 L 56.86 192 H 21.76 193 M 94.54 194 H 7.96 195 L60.39 196 H 0.75 197 M 85.58 198 H 14.24 199 L 20.74 200 H 30.65 201 M81.09 202 H 6.72 203 L 79.95 204 H 22.06 205 M 84.62 206 H 22.29 207 L111.33 208 H 42.05 209 M 50.04 210 H 33.07 211 L 108.85 212 H 31.63 213M 74.7 214 H 20.93 215 L 107.94 216 H 21.61 217 M 66.96 218 H 33.38 219L 103.68 220 H 24.5 221 M 68.85 222 H 38.65 223 L 105.43 224 H 23.6 225M 71.92 226 H 39.41 227 L 91.2 228 H 19.06 229 M 84.75 230 H 32.62 231 L53.42 232 H 11.05(nm)

TABLE 11 EXAMPLE 7 PRISM PBH56 H1 LAYER TiO₂ H2 LAYER Ta₂O₅ M LAYERAl₂O₃ L LAYER MgF₂ INCIDENT ANGLE 45 ± 5° FIRST BLUE WAVELENGTH BANDSECOND RED WAVELENGTH BAND LAYER FILM NUMBER METERIAL THICKNESS 1 M74.39 2 H1 16.73 3 L 78.47 4 H2 13.27 5 M 77.31 6 H1 7.82 7 L 83.94 8 H226.79 9 M 106.12 10 H1 26.56 11 L 35.88 12 H2 15.47 13 M 101.53 14 H110.88 15 L 83.23 16 H2 22.75 17 M 97.8 18 H1 40.98 19 L 40.66 20 H249.77 21 M 123.92 22 H1 25.53 23 L 65.93 24 H2 28.1 25 M 96.77 26 H15.08 27 L 66.07 28 H2 28.76 29 M 104.64 30 H1 29.44 31 L 55.47 32 H213.52 33 M 93.35 34 H1 7.18 35 L 95.98 36 H2 21.68 37 M 98.09 38 H138.47 39 L 13.68 40 H2 14.76 41 M 93.82 42 H1 10.89 43 L 113.53 44 H21.26 45 M 95.61 46 H1 4.25 47 L 96.78 48 H2 27.41 49 M 102.01 50 H133.17 51 L 36.35 52 H2 13.15 53 M 105.69 54 H1 8.88 55 L 90.82 56 H218.7 57 M 101.75 58 H1 19.07 59 L 52.79 60 H2 27.1 61 M 88.26 62 H119.25 63 L 50.96 64 H2 25.38 65 M 95.49 66 H1 23.76 67 L 40.19 68 H239.28 69 M 93.55 70 H1 14.06 71 L 58.44 72 H2 29.45 73 M 83.38 74 H122.92 75 L 77.55 76 H2 22.73 77 M 108.85 78 H1 32.3 79 L 34.18 80 H234.46 81 M 96.29 82 H1 11.53 83 L 91.15 84 H2 35.16 85 M 78.64 86 H126.62 87 L 44.91 88 H2 19.78 89 M 82.65 90 H1 35.83 91 L 57.71 92 H224.4 93 M 132.55 94 H1 56.4 95 L 19.1 96 H2 17.99 97 M 120.88 98 H1 0.1199 L 112.29 100 H2 20.63 101 M 91.97 102 H1 21.5 103 L 64.88 104 H218.51 105 M 104.7 106 H1 41.38 107 L 31.2 108 H2 30.6 109 M 102.1 110 H123.38 111 L 34.16 112 H2 46.31 113 M 87.92 114 H1 13.25 115 L 49.1 116H2 63.21 117 M 63.29 118 H1 25.86 119 L 66.82 120 H2 53.73 121 M 55.52122 H1 28.35 123 L 69.03 124 H2 58.62 125 M 61.18 126 H1 35.11 127 L75.84 128 H2 66.02 129 M 65.06 130 H1 29.52 131 L 66.69 132 H2 52.56 133M 55.79 134 H1 28.21 135 L 77.81 136 H2 50.78 137 M 55.01 138 H1 42.39139 L 74.07 140 H2 55.69 141 M 44.87 142 H1 40.5 143 L 52.48 144 H242.91 145 M 56.45 146 H1 42.07 147 L 45.32 148 H2 109.5 149 M 15.59 150H1 26.66 151 L 3.64

TABLE 12 EXAMPLE 8 PRISM S-LAH55 H LAYER TiO₂ M LAYER Al₂O₃ L LAYER MgF₂INCIDENT ANGLE 45 ± 2° FIRST BLUE WAVELENGTH BAND SECOND RED WAVELENGTHBAND LAYER FILM NUMBER MATERIAL THICKNESS 1 M 152.22 2 L 71.49 3 M173.34 4 H 24.18 5 M 152.08 6 L 128.01 7 M 139.44 8 H 38.04 9 M 134.4310 L 153.05 11 M 130.58 12 H 37.56 13 M 128.45 14 L 204.7 15 M 116.37 16H 47.66 17 M 115.53 18 L 206.51 19 M 121.15 20 H 43.08 21 M 123.87 22 L195.76 23 M 112.73 24 H 58.22 25 M 105.01 26 L 202.96 27 M 116.41 28 H50.02 29 M 124.79 30 L 169.06 31 M 130.68 32 H 56.79 33 M 152.96 34 L122.8 35 M 172.4 36 H 15 37 L 17.03 38 H 46.99 39 M 98.21 40 H 15 41 L118.64 42 H 28.44 43 M 93.76 44 H 17.96 45 L 95.72 46 H 26.23 47 M 81.6248 H 30.05 49 L 126.35 50 H 33.3 51 M 69.05 52 H 36.43 53 L 110.09 54 H33.97 55 M 60.1 56 H 34.1 57 L 85.72 58 H 24.37 59 M 78.42 60 H 35.69 61L 113.53 62 H 15.16 63 M 128.04 64 H 22.6 65 L 34.67(nm)

TABLE 13 EXAMPLE 9 PRISM S-LAH55 H LAYER TiO₂ M LAYER Al₂O₃ L LAYER MgF₂INCIDENT ANGLE 45 ± 2° FIRST BLUE WAVELENGTH BAND SECOND RED WAVELENGTHBAND LAYER FILM NUMBER MATERIAL THICKNESS 1 M 160.04 2 L 88.86 3 M172.22 4 H 32.53 5 M 156.68 6 L 125.64 7 M 147.62 8 H 31.14 9 M 147.2410 L 146.48 11 M 136.3 12 H 45.08 13 M 131.78 14 L 200.26 15 M 129.64 16H 44.92 17 M 125.52 18 L 182.86 19 M 127.71 20 H 45.17 21 M 130.32 22 L215.91 23 M 129.55 24 H 49.36 25 M 129 26 L 154.2 27 M 135.74 28 H 47.529 M 139.3 30 L 156.4 31 M 134.38 32 H 64.35 33 M 148.16 34 L 145.67 35M 154.6 36 H 65.19 37 M 147.8 38 L 164.92 39 M 148.46 40 H 64.49 41 M148.32 42 L 159.44 43 M 153.92 44 H 65.86 45 M 150.29 46 L 175.25 47 M150.17 48 H 64.19 49 M 148.56 50 L 152.2 51 M 168.21 52 H 19.24 53 M436.52 54 L 103.34 55 M 92.74 56 H 118.36 57 M 72.01 58 L 105.84 59 M28.98 60 H 124.08 61 M 95.07 62 L 111.28 63 M 63.11(nm)

TABLE 14 EXAMPLE 10 FIFTH MULTILAYER FILM PRISM S-LAH55 H LAYER TiO₂ MLAYER Al₂O₃ L LAYER MgF₂ INCIDENT ANGLE 45 ± 2° FIRST BLUE WAVELENGTHBAND SECOND RED WAVELENGTH BAND LAYER FILM NUMBER MATERIAL THICKNESS 1 M160.04 2 L 88.86 3 M 172.22 4 H 32.53 5 M 156.68 6 L 125.64 7 M 147.62 8H 31.14 9 M 147.24 10 L 146.48 11 M 136.3 12 H 45.08 13 M 131.78 14 L200.26 15 M 129.64 16 H 44.92 17 M 125.52 18 L 182.86 19 M 127.71 20 H45.17 21 M 130.32 22 L 215.91 23 M 129.55 24 H 49.36 25 M 129 26 L 154.227 M 135.74 28 H 47.5 29 M 139.3 30 L 156.4 31 M 134.38 32 H 64.35 33 M148.16 34 L 145.67 35 M 154.6 36 H 65.19 37 M 147.8 38 L 164.92 39 M148.46 40 H 64.49 41 M 148.32 42 L 159.44 43 M 153.92 44 H 65.86 45 M150.29 46 L 175.25 47 M 150.17 48 H 64.19 49 M 148.56 50 L 152.2 51 M168.21 52 H 19.24 53 M 436.52 54 L 103.34 55 M 92.74 56 H 118.36 57 M72.01 58 L 105.84 59 M 28.98 60 H 124.08 61 M 95.07 62 L 111.28 63 M63.11(nm)

TABLE 15 EXAMPLE 10 THIRD MULTILAYER FILM PRISM S-LAH55 H LAYER Ta₂O₅ LLAYER Al₂O₃ INCIDENT ANGLE 45 ± 2° FIRST WAVELENGTH BAND BLUE SECONDWAVELENGTH BAND RED LAYER NUMBER MATERIAL FILM THICKNESS 1 L 46.22 2 H143.62 3 L 76.75 4 H 132.79 5 L 96.29 6 H 126.37 7 L 98.49 8 H 122.26 9L 102.47 10 H 124.2 11 L 131.06 12 H 126.09 13 L 145.13(nm)

TABLE 16 EXAMPLE 11 PRISM S-LAH55 H LAYER TiO₂ M LAYER Al₂O₃ L LAYERMgF₂ INCIDENT ANGLE 45° FIRST WAVELENGTH BAND BLUE SECOND WAVELENGTHBAND RED LAYER NUMBER MATERIAL FILM THICKNESS 1 H 32.17 2 L 50.59 3 M126.48 4 L 67.2 5 H 81.8 6 L 53.46 7 M 122.26 8 L 24.94 9 H 55.29 10 L10.2 11 M 102.96 12 L 179.91 13 H 18.77 14 L 23.41 15 M 89.33 16 L116.35 17 H 16.07 18 L 104.14 19 M 107.03 20 L 175.75 21 H 10 22 L 49.4623 M 106.18 24 L 144.51 25 H 10 26 L 93.96 27 M 107.54 28 L 104.12 29 H11.47 30 L 137.83 31 M 107.68 32 L 88.54 33 H 11.42 34 L 142.16 35 M105.07 36 L 114.77 37 H 26.14 38 L 82.63 39 M 103.54 40 L 184.4(nm)

TABLE 17 EXAMPLE 12 PRISM S-LAH55 H LAYER TiO₂ M LAYER Al₂O₃ L LAYERMgF₂ INCIDENT ANGLE 45 ± 2° FIRST BLUE WAVELENGTH BAND SECOND REDWAVELENGTH BAND LAYER FILM NUMBER MATERIAL THICKNESS 1 H 10.54 2 L 61.93 M 146.54 4 L 10.1 5 H 85.33 6 L 44.89 7 M 123.62 8 L 57.47 9 H 36.5410 L 35.95 11 M 136.27 12 L 75.06 13 H 24.42 14 L 36.59 15 M 140.66 16 L90.83 17 H 30.48 18 L 25.71 19 M 159.82 20 L 108.21 21 H 36.1 22 L 10 23M 80.58 24 L 18 25 H 15.73 26 L 123.02 27 M 154.04 28 L 56.22 29 H 10 30L 89.07 31 M 145.08 32 L 42.49 33 H 21.86 34 L 79.01 35 M 144.7 36 L43.36 37 H 15.16 38 L 81.05 39 M 157.24 40 L 45.98 41 H 18.2 42 L 73.6943 M 138.9 44 L 28.12 45 H 26.13 46 L 68.66 47 M 142.26 48 L 61.34 49 H20.5 50 L 51.78 51 M 113.97 52 L 60.95 53 H 20.74 54 L 41.45 55 M 108.4256 L 77.69 57 H 12.82 58 L 66.79 59 M 127.23 60 L 67.78 61 H 12.31 62 L73.12 63 M 126.35 64 L 50.7 65 H 13.37 66 L 73.82 67 M 123.04 68 L 56.3469 H 13.96 70 L 77.49 71 M 123.52 72 L 42.17 73 H 32.52 74 L 36.45 75 M106.48 76 L 48.56 77 H 10 78 L 91.94 79 M 136.58 80 L 58.74 81 H 14.8182 L 18.85 83 M 129.53 84 L 74.36 85 H 10 86 L 86.37 87 M 106 88 L 32.7489 H 20.4 90 L 47.22 91 M 140.69 92 L 60.09 93 H 18.14 94 L 23.94 95 M108 96 L 11.61 97 H 16.34 98 L 146.54 99 M 181.46 100 L 50.18(nm)

TABLE 18 EXAMPLE 13 PRISM S-LAH55 H1 LAYER TiO₂ M LAYER Al₂O₃ L LAYERMgF₂ INCIDENT ANGLE 45 ± 2° FIRST BLUE WAVELENGTH BAND SECOND REDWAVELENGTH BAND LAYER FILM NUMBER MATERIAL THICKNESS 1 M 27.8 2 H 110.653 M 157 4 H 102.94 5 M 116.18 6 H 102.63 7 M 171.4 8 H 108.58 9 M 195.4710 H 102.74 11 M 140.76 12 H 106.87 13 M 200 14 H 10 15 L 58.93 16 M143.04 17 L 30.44 18 H 22.3 19 L 10.76 20 M 201.74 21 L 37.6 22 H 29.0423 L 13.65 24 M 178.38 25 L 51.66 26 H 29.98 27 L 28.04 28 M 147.75 29 L113.16 30 H 30.22 31 L 10 32 M 94.71 33 L 10 34 H 18.84 35 L 96.43 36 M178.44 37 L 69.74 38 H 23.12 39 L 49.38 40 M 157.54 41 L 82.48 42 H19.06 43 L 43.06 44 M 146.44 45 L 134.28 46 H 15.27 47 L 10 48 M 117.9949 L 10 50 H 16.08 51 L 111.53 52 M 143.45 53 L 16.12 54 H 21.7 55 L76.92 56 M 157.05 57 L 26.02 58 H 33.38 59 L 54.31 60 M 165.5 61 L 31 62H 26.53 63 L 65.5 64 M 127.67 65 L 62.49 66 H 28.12 67 L 35.5 68 M110.92 69 L 51.71 70 H 10.9 71 L 75.34 72 M 112.15 73 L 89.74 74 H 14.5975 L 54.84 76 M 123 77 L 61.44 78 H 12.26 79 L 85 80 M 118.54 81 L 57.9982 H 13.54 83 L 93.41 84 M 109.89 85 L 49.53 86 H 24.9 87 L 79.87 88 M111.74 89 L 74.13 90 H 27.13 91 L 49.48 92 M 98.69 93 L 108.9 94 H 10 95L 53.47 96 M 95.36 97 L 43.7 98 H 10.78 99 L 108.93 100 M 101.99 101 L61.46 102 H 25.7 103 L 80.39 104 M 117.64 105 L 84.62 106 H 20.25 107 L53.43 108 M 85.03 109 L 96.44 110 H 10 111 L 80.49 112 M 113.28 113 L29.28 114 H 23.9 115 L 32 116 M 149.35 117 L 42.93(nm)

TABLE 19 EXAMPLE 1 2 3 4 5 GENERAL STRUCTURE OF MULTILAYER FILM HMHLHMHL HMHL HMHL HMHL REFRACTIVE INDEX OF P 1.85 1.85 1.85 1.85 1.85INCIDENT-SIDE (PRISM MATERIAL OF PBH56 PBH56 PBH56 PBH56 PBH56INCIDENT-SIDE (PRISM REFRACTIVE INDEX OF H 2.32 2.32 2.32 2.32 2.32 HIGHREFRACTIVE INDEX LAYER REFRACTIVE INDEX OF M 1.65 1.65 1.65 1.8 1.8MIDDLE REFRACTIVE INDEX LAYER 1.65 REFRACTIVE INDEX OF L 1.39 1.39 1.491.39 1.49 LOW REFRACTIVE INDEX LAYER 1.49 REFRACTIVE INDEX OF ADHESIVE1.55 1.55 1.55 1.55 1.55 EMERGENCE-SIDE (ADHESIVE) REFRACTIVE INDEXDIFFERENCE 0.67 0.67 0.67 0.52˜0.67 0.52 BETWEEN HIGH REFRACTIVE INDEXLAYER AND MIDDLE REFRACTIVE INDEX LAYER REFRACTIVE INDEX DIFFERENCE 0.260.26 0.16 0.16˜0.41 0.31 BETWEEN MIDDLE REFRACTIVE INDEX LAYER AND LOWREFRACTIVE INDEX LAYER TRANSMITTANCE (%) OF P-POLARIZED 5.71  1.38˜26.45 0.57˜18.47 92.17˜99.78  0.83˜29.80 LIGHT AT WAVELENGTH OF 430 NMTRANSMITTANCE (%) OF S-POLARIZED 98.17 91.88˜98.64 93.10˜97.96 0.0089.04˜91.60 LIGHT AT WAVELENGTH OF 430 NM TRANSMITTANCE DIFFERENCE (%)92.46 85.43˜97.28 74.63˜97.38 92.16˜99.76 61.80˜90.47 BETWEENS-POLARIZED LIGHT AND P-POLARIZED LIGHT AT WAVELENGTH OF 430 NMTRANSMITTANCE (%) OF P-POLARIZED 2.62  3.13˜21.72  9.66˜22.7774.06˜97.55  8.94˜30.88 LIGHT AT WAVELENGTH OF 490 NM TRANSMITTANCE (%)OF S-POLARIZED 95.04 82.84˜96.77 92.48˜96.72 0.04˜3.71 82.66˜96.58 LIGHTAT WAVELENGTH OF 490 NM TRANSMITTANCE DIFFERENCE (%) 92.42 71.21˜83.2470.33˜87.06 72.15˜97.51 63.74˜81.41 BETWEEN S-POLARIZED LIGHT ANDP-POLARIZED LIGHT AT WAVELENGTH OF 490 NM TRANSMITTANCE (%) OFP-POLARIZED 96.81 86.99˜93.55 81.32˜93.55  0.71˜27.46 89.18˜82.34 LIGHTAT WAVELENGTH OF 580 NM (585 NM IN EXAMPLE 4) TRASMITTANCE (%) OFS-POLARIZED 0.51  0.02˜13.64 0.00˜1.81 96.42˜99.86  0.31˜12.48 LIGHT ATWAVELENGTH OF 580 NM (585 NM IN EXAMBLE 4) TRANSMITTANCE DIFFERENCE (%)96.29 73.35˜93.53 79.52˜93.51 70.69˜98.16 79.85˜89.17 BETWEENS-POLARIZED LIGHT AND P-POLARIZED LIGHT AT WAVELENGTH OF 580 NM (585 NMIN EXAMBLE 4) TRANSMITTANCE (%) OF P-POLARIZED 99.74 93.55˜99.3288.70˜97.06  9.49˜20.46 90.13˜99.82 LIGHT AT WAVELENGTH OF 650 NMTRANSMITTANCE (%) OF P-POLARIZED 3.45 1.01˜6.78 0.04˜5.35 93.48˜99.32 2.65˜14.73 LIGHT AT WAVELENGTH OF 650 NM TRANSMITTANCE DIFFERENCE (%)96.29 80.33˜85.33 76.52˜85.36 76.52˜85.35 75.41˜85.93 BETWEENS-POLARIZED LIGHT AND P-POLARIZED LIGHT AT WAVELENGTH OF 650 NM EXAMPLE6 7 8 9 GENERAL STRUCTURE OF MULTILAYER FILM HMHL HMHL MLMH MLMHREFRACTIVE INDEX OF P 1.7 1.85 1.84 1.84 INCIDENT-SIDE (PRISM MATERIALOF S-LAL14 PBH56 S-LAH55 S-LAH55 INCIDENT-SIDE (PRISM REFRACTIVE INDEXOF H 2.32 2.32 2.32 2.32 HIGH REFRACTIVE INDEX LAYER 2.15 REFRACTIVEINDEX OF M 1.65 1.65 1.65 1.65 MIDDLE REFRACTIVE INDEX LAYER REFRACTIVEINDEX OF L 1.39 1.39 1.39 1.39 LOW REFRACTIVE INDEX LAYER REFRACTIVEINDEX OF ADHESIVE 1.55 1.55 1.55 1.55 EMERGENCE-SIDE (ADHESIVE)REFRACTIVE INDEX DIFFERENCE 0.67  0.5˜0.67 0.67 0.67 BETWEEN HIGHREFRACTIVE INDEX LAYER AND MIDDLE REFRACTIVE INDEX LAYER REFRACTIVEINDEX DIFFERENCE 0.26 0.26 0.26 0.26 BETWEEN MIDDLE REFRACTIVE INDEXLAYER AND LOW REFRACTIVE INDEX LAYER TRANSMITTANCE (%) OF P-POLARIZED 0.30˜18.54  0.40˜16.71 0.27˜7.99 0.11˜7.96 LIGHT AT WAVELENGTH OF 430NM TRANSMITTANCE (%) OF S-POLARIZED 82.38˜96.98 91.33˜93.38 94.28˜95.0294.77˜98.53 LIGHT AT WAVELENGTH OF 430 NM TRANSMITTANCE DIFFERENCE (%)73.84˜96.68 75.40˜92.57 86.85˜94.60 86.80˜96.41 BETWEEN S-POLARIZEDLIGHT AND P-POLARIZED LIGHT AT WAVELENGTH OF 430 NM TRANSMITTANCE (%) OFP-POLARIZED  7.37˜18.76  4.43˜18.88 5.08˜7.13 5.48˜9.12 LIGHT ATWAVELENGTH OF 490 NM TRANSMITTANCE (%) OF S-POLARIZED 91.05˜99.9685.88˜97.04 94.33˜96.91 94.73˜98.05 LIGHT AT WAVELENGTH OF 490 NMTRANSMITTANCE DIFFERENCE (%) 72.29˜81.39 78.15˜83.59 87.95˜91.8085.61˜89.66 BETWEEN S-POLARIZED LIGHT AND P-POLARIZED LIGHT ATWAVELENGTH OF 490 NM TRANSMITTANCE (%) OF P-POLARIZED 87.28˜98.3091.09˜96.86 94.52˜95.26 93.10˜99.30 LIGHT AT WAVELENGTH OF 580 NM (585NM IN EXAMPLE 4) TRASMITTANCE (%) OF S-POLARIZED 0.27˜4.48  0.07˜19.750.04˜3.72 1.08˜3.60 LIGHT AT WAVELENGTH OF 580 NM (585 NM IN EXAMBLE 4)TRANSMITTANCE DIFFERENCE (%) 87.01˜96.70 73.67˜98.58 90.81˜95.2289.30˜96.94 BETWEEN S-POLARIZED LIGHT AND P-POLARIZED LIGHT ATWAVELENGTH OF 580 NM (585 NM IN EXAMBLE 4) TRANSMITTANCE (%) OFP-POLARIZED 88.75˜99.47 86.90˜99.30 94.79˜99.91 94.87˜99.09 LIGHT ATWAVELENGTH OF 650 NM TRANSMITTANCE (%) OF P-POLARIZED 1.76˜6.161.57˜4.79 0.00˜5.25 0.01˜5.34 LIGHT AT WAVELENGTH OF 650 NMTRANSMITTANCE DIFFERENCE (%) 86.46˜97.71 84.22˜95.18 94.66˜94.7991.47˜94.86 BETWEEN S-POLARIZED LIGHT AND P-POLARIZED LIGHT ATWAVELENGTH OF 650 NM EXAMPLE 10 11 12 13 GENERAL STRUCTURE OF MULTILAYERFILM MLMH LMLH LMLH LMLH REFRACTIVE INDEX OF P 1.84 1.84 1.84 1.84INCIDENT-SIDE (PRISM MATERIAL OF S-LAH55 S-LAH55 S-LAH55 S-LAH55INCIDENT-SIDE (PRISM REFRACTIVE INDEX OF H 2.15 2.32 2.32 2.32 HIGHREFRACTIVE INDEX LAYER REFRACTIVE INDEX OF M 1.65 1.65 1.65 1.65 MIDDLEREFRACTIVE INDEX LAYER REFRACTIVE INDEX OF L 1.39 1.39 1.39 1.39 LOWREFRACTIVE INDEX LAYER REFRACTIVE INDEX OF ADHESIVE 1.55 1.55 1.55 1.55EMERGENCE-SIDE (ADHESIVE) REFRACTIVE INDEX DIFFERENCE 0.5 0.67 0.67 0.67BETWEEN HIGH REFRACTIVE INDEX LAYER AND MIDDLE REFRACTIVE INDEX LAYERREFRACTIVE INDEX DIFFERENCE 0.26 0.26 0.26 0.26 BETWEEN MIDDLEREFRACTIVE INDEX LAYER AND LOW REFRACTIVE INDEX LAYER TRANSMITTANCE (%)OF P-POLARIZED  0.72˜18.01 3.79 0.62˜8.02 0.13˜5.21 TRANSMITTANCE (%) OFS-POLARIZED LIGHT AT WAVELENGTH OF 430 NM 94.40˜96.98 96.93 94.01˜98.4194.92˜97.85 TRANSMITTANCE DIFFERENCE (%) BETWEEN S-POLARIZED LIGHT AND78.08˜96.23 93.14 86.86˜97.79 89.74˜96.94 P-POLARIZED LIGHT ATWAVELENGTH OF 430 NM TRANSMITTANCE (%) OF P-POLARIZED LIGHT ATWAVELENGTH OF 490 NM 10.89˜15.62 3.49 5.64˜8.92 4.47˜5.59 TRANSMITTANCE(%) OF S-POLARIZED LIGHT AT WAVELENGTH OF 490 NM 94.95˜97.41 96.5794.38˜95.73 94.96˜98.98 TRANSMITTANCE DIFFERENCE (%) BETWEEN S-POLARIZEDLIGHT AND 79.33˜84.90 93.09 85.52˜90.09 89.38˜94.24 P-POLARIZED LIGHT ATWAVELENGTH OF 490 NM TRANSMITTANCE (%) OF P-POLARIZED LIGHT ATWAVELENGTH OF 580 NM 91.28˜97.42 98.72 92.68˜7.81  94.84˜98.72 (585 NMIN EXAMPLE 4) TRASMITTANCE (%) OF S-POLARIZED LIGHT AT WAVELENGTH OF 580NM 2.36˜9.33 0.77 0.14˜3.36 0.11˜0.35 (585 NM IN EXAMBLE 4)TRANSMITTANCE DIFFERENCE (%) BETWEEN S-POLARIZED LIGHT AND 83.85˜93.2897.95 89.32˜87.77 84.49˜98.43 P-POLARIZED LIGHT AT WAVELENGTH OF 580 NM(585 NM IN EXAMBLE 4) TRANSMITTANCE (%) OF P-POLARIZED LIGHT ATWAVELENGTH OF 650 NM 92.04˜99.32 97.66 98.46˜98.96 95.64˜98.72TRANSMITTANCE (%) OF P-POLARIZED LIGHT AT WAVELENGTH OF 650 NM 0.01˜5.343.29 4.95˜5.63 0.01˜0.49 TRANSMITTANCE DIFFERENCE (%) BETWEENS-POLARIZED LIGHT AND 92.03˜95.32 94.37 92.83˜94.01 95.15˜98.72P-POLARIZED LIGHT AT WAVELENGTH OF 650 NM

1. A polarization beam splitter comprising: a multilayer film formed bylaminating a first layer having a refractive index in a first range, asecond layer having a refractive index in a second range which does notoverlap the first range, and a third layer having a refractive index ina third range which does not overlap the first or second range in theorder of the first layer, the second layer, the first layer, and thethird layer, wherein the transmittance of s-polarized light is 60% ormore higher than the transmittance of p-polarized light in a firstwavelength region, the transmittance of p-polarized light is equal to orhigher than 70% in a second wavelength region different from the firstwavelength region, and each of the first wavelength region and thesecond wavelength region has a bandwidth equal to or larger than 30 nm.2. A polarization beam splitter comprising: a multilayer film formed bylaminating a first layer having a refractive index in a first range, asecond layer having a refractive index in a second range which does notoverlap the first range, and a third layer having a refractive index ina third range which does not overlap the first or second range in theorder of the first layer, the second layer, the first layer, and thethird layer, wherein the transmittance of s-polarized light is 60% ormore higher than the transmittance of p-polarized light in a firstwavelength region, the transmittance of p-polarized light is 60% or morehigher than the transmittance of s-polarized light in a secondwavelength region different from the first wavelength region, and eachof the first wavelength region and the second wavelength region has abandwidth equal to or larger than 30 nm.
 3. The polarization beamsplitter according to claim 2, wherein the multilayer film is amultilayer film formed by laminating the first layer, the second layer,the first layer, and the third layer in this order in succession fivetimes or more.
 4. The polarization beam splitter according to claim 2,wherein the first wavelength region and the second wavelength region areincluded in region of visible wavelength (400 nm or higher and 700 nm orlower).
 5. The polarization beam splitter according to claim 2, whereinthe first wavelength region includes a band of 450 nm to 480 nm and thesecond wavelength region includes a band of 600 nm to 630 nm.
 6. Thepolarization beam splitter according to claim 2, wherein, when a layerof the first, second, and third layers with the highest refractive indexis an H layer (a high refractive index layer), a layer of the threelayers with the second highest refractive index is an M layer (a middlerefractive index layer), and a layer of the three layers with the lowestrefractive index is an L layer (a low refractive index layer), then thehigh refractive index layer has a refractive index of 2.0 or higher and2.6 or lower, the middle refractive index layer has a refractive indexof 1.59 or higher and 1.9 or lower, and the low refractive index layerhas a refractive index of 1.25 or higher and 1.56 or lower.
 7. Thepolarization beam splitter according to claim 2, wherein, when a layerof the first, second, and third layers with the highest refractive indexis an H layer (a high refractive index layer), a layer of the threelayers with the second highest refractive index is an M layer (a middlerefractive index layer), and a layer of the three layers with the lowestrefractive index is an L layer (a low refractive index layer), then thedifference in the refractive index between the high refractive indexlayer and the middle refractive index layer is 0.35 or higher and 0.9 orlower, and the difference in the refractive index between the middlerefractive index layer and the lower refractive index layer is 0.12 orhigher and 0.55 or lower.
 8. The polarization beam splitter according toclaim 2, wherein the multilayer film is sandwiched between a substancemade of a first material having a refractive index of 1.55 or higher and2.10 or lower and a substance made of a second material having arefractive index of 1.40 or higher and 1.70 or lower.
 9. Thepolarization beam splitter according to claim 2, wherein at least one ofthe first layer, the second layer, and the third layer includes twolayers having refractive indexes different from each other.
 10. Thepolarization beam splitter according to claim 2, wherein the first rangecorresponds to the highest range of refractive indexes of the first,second, and third ranges.
 11. The polarization beam splitter accordingto claim 10, wherein, when a layer of the first, second, and thirdlayers with the highest refractive index is an H layer, a layer of thethree layers with the second highest refractive index is an M layer, alayer of the three layers with the lowest refractive index is an Llayer, the refractive indexes of the H layer, L layer, and M layer arerepresented as n_(H), n_(L), and n_(M), a design wavelength isrepresented as λ, the multilayer film is formed by laminating the firstH layer, the M layer, the second H layer, and the L layer in this orderin succession, and the film thickness of the first H layer, the M layer,the second H layer, and the L layer are represented as b×λ/(4n_(H)),c×λ/(4n_(M)), d×λ/(4n_(H)), a×λ/(4n_(L)), then 0<a<3, 0<b≦1, 0<c<5, and0<d≦1 are satisfied.
 12. The polarization beam splitter according toclaim 10, wherein, when a layer of the first, second, and third layerswith the highest refractive index is an H layer, a layer of the threelayers with the second highest refractive index is an M layer, a layerof the three layers with the lowest refractive index is an L layer, therefractive indexes of the H layer, L layer, and M layer are representedas n_(H), n_(L), and n_(M), a design wavelength is represented as λ, themultilayer film is formed by laminating the first H layer, the M layer,the second H layer, and the L layer in this order in succession, and thefilm thickness of the first H layer, the M layer, the second H layer,and the L layer are represented as b×λ/(4n_(H)), c×λ/(4n_(M)),d×λ/(4n_(H)), a×λ/(4n_(L)), then 0<b≦a≦c<5, 0<d≦a≦c<5 are satisfied. 13.The polarization beam splitter according to claim 2, wherein the firstrange corresponds to the second highest range of refractive indexes ofthe first, second, and third ranges.
 14. The polarization beam splitteraccording to claim 13, wherein, when a layer of the first, second, andthird layers with the highest refractive index is an H layer, a layer ofthe three layers with the second highest refractive index is an M layer,a layer of the three layers with the lowest refractive index is an Llayer, the refractive indexes of the H layer, L layer, and M layer arerepresented as n_(H), n_(L), and n_(M), a design wavelength isrepresented as λ, the multilayer film is formed by laminating the firstM layer, the L layer, the second M layer, and the H layer in this orderin succession, and the film thickness of the first M layer, the L layer,the second M layer, and the H layer are represented as a×λ/(4nm),b×λ/(4n_(L)), c×λ/(4n_(M)), d×λ/(4n_(H)), then 0<a<6, 0<c<6, d<b, 0<b<5,and 0<d<2 are satisfied.
 15. The polarization beam splitter according toclaim 13, wherein, when a layer of the first, second, and third layerswith the highest refractive index is an H layer, a layer of the threelayers with the second highest refractive index is an M layer, a layerof the three layers with the lowest refractive index is an L layer, therefractive indexes of the H layer, L layer, and M layer are representedas n_(H), n_(L), and n_(M), a design wavelength is represented as λ, themultilayer film is formed by laminating the first M layer, the L layer,the second M layer, and the H layer in this order in succession, and thefilm thickness of the first M layer, the L layer, the second M layer,and the H layer are represented as a×λ/(4n_(M)), b×λ/(4n_(L)),c×λ/(4n_(M)), d×λ/(4n_(H)), then 0<a<3, 0<c<6, d<b, 0<b<2, and 0<d<1 aresatisfied.
 16. The polarization beam splitter according to claim 2,wherein the first range corresponds to the lowest range of refractiveindexes of the first, second, and third ranges.
 17. The polarizationbeam splitter according to claim 16, wherein, when a layer of the first,second, and third layers with the highest refractive index is an Hlayer, a layer of the three layers with the second highest refractiveindex is an M layer, a layer of the three layers with the lowestrefractive index is an L layer, the refractive indexes of the H layer, Llayer, and M layer are represented as n_(H), n_(L), and n_(M), a designwavelength is represented as λ, the multilayer film is formed bylaminating the first L layer, the H layer, the second L layer, and the Mlayer in this order in succession, and the film thickness of the first Llayer, the H layer, the second L layer, and the M layer are representedas a×λ/(4n_(L)), b×λ/(4n_(H)), c×λ/(4n_(L)), d×λ/(4n_(M)), then 0<a<3,0<b<5, d<b, 0<c<3, and 0<d≦1 are satisfied.
 18. The polarization beamsplitter according to claim 16, wherein, when a layer of the first,second, and third layers with the highest refractive index is an Hlayer, a layer of the three layers with the second highest refractiveindex is an M layer, a layer of the three layers with the lowestrefractive index is an L layer, the refractive indexes of the H layer, Llayer, and M layer are represented as n_(H), n_(L), and n_(M), a designwavelength is represented as λ, the multilayer film is formed bylaminating the first L layer, the H layer, the second L layer, and the Mlayer in this order in succession, and the film thickness of the first Llayer, the H layer, the second L layer, and the M layer are representedas a×λ/(4n_(L)), b×λ/(4n_(H)), c×λ/(4n_(L)), d×λ/(4n_(M)), then0<b≦a≦c<5, 0<d≦a≦c<5 are satisfied.
 19. An image display apparatuscomprising: a first image display device; a second image display device;and a color combination optical system which combines first image lightemerging from the first image display device and second image lightemerging from the second image display device, wherein the colorcombination optical system has the polarization beam splitter accordingto claim
 1. 20. An image display apparatus comprising: a firstreflection type liquid crystal display device which is provided forfirst color light; a second reflection type liquid crystal displaydevice which is provided for second color light different from the firstcolor light; an illumination optical system which illuminates the firstand second reflection type liquid crystal display devices with lightfrom a light source; and a projection optical system which projectslight from the first and second reflection type liquid crystal displaydevices to a projected surface, wherein the illumination optical systemincludes the polarization beam splitter according to claim 1, and thefirst color light in a first polarization state and the second colorlight in the first polarization state are directed to the polarizationbeam splitter to illuminate the first reflection type liquid crystaldisplay device with the first color light in the first polarizationstate and illuminate the second reflection type liquid crystal displaydevice with the second color light in the first polarization state, andthe polarization beam splitter color-combines the first color light in asecond polarization state and the second color light in the secondpolarization state emerging from the first reflection type liquidcrystal display device and the second reflection type liquid crystaldisplay device, respectively, to direct the combined light to theprojection optical system, the second polarization state showing apolarization direction orthogonal to the first polarization state. 21.An image display apparatus comprising: a first image display device; asecond image display device; a color combination optical system whichcombines first image light emerging from the first image display deviceand second image light emerging from the second image display device,wherein the color combination optical system has the polarization beamsplitter according to claim
 2. 22. An image display apparatuscomprising: a first reflection type liquid crystal display device whichis provided for first color light; a second reflection type liquidcrystal display device which is provided for second color lightdifferent from the first color light; an illumination optical systemwhich illuminates the first and second reflection type liquid crystaldisplay devices with light from a light source; and a projection opticalsystem which projects light from the first and second reflection typeliquid crystal display devices to a projected surface, wherein theillumination optical system includes the polarization beam splitteraccording to claim 2, and the first color light in a first polarizationstate and the second color light in the first polarization state aredirected to the polarization beam splitter to illuminate the firstreflection type liquid crystal display device with the first color lightin the first polarization state and illuminate the second reflectiontype liquid crystal display device with the second color light in thefirst polarization state, and the polarization beam splittercolor-combines the first color light in a second polarization state andthe second color light in the second polarization state emerging fromthe first reflection type liquid crystal display device and the secondreflection type liquid crystal display device, respectively, to directthe combined light to the projection optical system, the secondpolarization state showing a polarization direction orthogonal to thefirst polarization state.